By Ned Parker and Maria Golovnina
WASHINGTON/ISLAMABAD, June 13 (Reuters) - - In Iraq, an al Qaeda splinter group is threatening Baghdad after seizing control of two cities. In Pakistan, the Taliban attacked a major airport twice in one week. And in Nigeria, the Islamist militant group Boko Haram was blamed for another mass kidnapping.
A cluster of militant attacks over the past week is a reminder of how the once-singular threat of al Qaeda has changed since the killing of Osama bin Laden, morphing or splintering into smaller, largely autonomous Islamist factions that in some cases are now overshadowing the parent group.
Each movement is different, fueled by local political and sectarian dynamics. But this week's violence is a measure of their ambition and the long-term potential danger they pose to the West.
Between 2010 and 2013, the number of al Qaeda and al Qaeda-related groups rose 58 percent and the number of "Salafi jihadists" - violent proponents of an extreme form of Islam - more than doubled, according to a report by the RAND Corp think tank.
Daniel Benjamin, former U.S. State Department counterterrorism coordinator under President Barack Obama, said he was "considerably more optimistic 18 months ago than ... now" about the threat posed by al Qaeda-related groups.
Few examples are more vivid than the fall of northern Iraq, which has raised the prospect of the country's disintegration as a unified state.
Sunni insurgents known as the Islamic State of Iraq and the Levant, or ISIL, seized the northern city of Mosul on Tuesday, and then overran an area further south on Wednesday, capturing the city of Tikrit and threatening Iraq's capital, Baghdad.
The militants are exploiting deep resentment among Iraq's Sunni minority, which lost power when the 2003 U.S.-led invasion toppled Saddam Hussein. Since the U.S. withdrawal in 2011, the Sunni population has become increasingly alienated from Prime Minister Nouri al-Maliki's Shii'ite-dominated government and his U.S.-trained military.
This has helped fuel the stunning resurgence of ISIL. The group seeks to create a caliphate based on medieval Sunni Islamic principles across Iraq and neighboring Syria, where it has become one of the fiercest rebel forces in the civil war to oust President Bashar al-Assad.
ISIL underscores the complexity of the new galaxy of militant groups. Earlier this year, it split from the core al Qaeda organization completely, after a dispute between ISIL's leader and bin Laden's successor, Ayman al-Zawahiri.
"WE ARE TALKING ABOUT YEARS"
Even if Iraq can survive the onslaught, there is no saying how long it might take to restore order. "This is a very protracted war against terror," said an adviser to Maliki. "We are not talking about months. We are talking about years."
It has taken years for the situation to reach its current low point. After the 2003 Iraq invasion, the disgruntled Sunni population initially served as the base for a bloody insurgency against the U.S. military and emerging Shi'ite majority rule.
That revolt appeared to have been quelled by the time U.S. troops left in December 2011. But Iraqi Sunni grievances simmered, fanned by what they saw as Maliki's sectarian rule and failure to build an inclusive government and army.
The future members of ISIL, then calling themselves the Islamic State of Iraq, were ready when the uprising in Syria started in 2011 and moved in to take advantage of the chaos. Bolstered by their success on the battlefield, they renamed themselves the Islamic State of Iraq and the Levant.
With ISIL's lightning advance in Iraq in recent days, the army has seen thousands of soldiers desert their posts in the north. And in Baghdad, fears of a sectarian bloodbath have grown.
Benjamin, now at Dartmouth University, said that groups like ISIL and rival Jabhat al-Nusrah in Syria, while serious regional problems, do not pose the same direct threat to the United States and its allies that bin Laden's al Qaeda did.
"We shouldn't lose sight of that," he said. "I don't think it's an existential threat by any means."
TENSIONS HIGH IN PAKISTAN
Tensions are also running high in Pakistan, where a brazen attack by the Pakistani Taliban on the country's biggest airport in Karachi underscored the resurgence of an Islamist group with longtime ties to al Qaeda. Ten militants were killed in a gun battle that claimed at least 34 other lives.
The Pakistani Taliban has vowed a large-scale campaign against government and security installations after months of failed peace negotiations. In response, the Pakistani army is expected to ramp up air strikes in restive tribal areas.
So far, cities like Islamabad and Lahore have not seen the kind of violence that has plagued other parts of the country. But observers expect that to change.
The Pakistani Taliban operate closely with al Qaeda, which has senior commanders deployed in the tribal areas, as well as the Afghan Taliban, who provide their Pakistani comrades with funding and logistical support.
Prime Minister Nawaz Sharif has long advocated peace talks with the Taliban but the picture changed radically after the airport attack, with public opinion swinging back again in favour of an all-out military operation against the militants.
Signaling possible escalation, U.S. drones struck Taliban hideouts in Pakistan, killing at least 10 militants in response to the Karachi airport attack, officials said on Thursday, in the first such raids by unmanned CIA aircraft in six months.
Pakistani government officials said Islamabad had given the Americans "express approval" for the strikes - the first time Pakistan has admitted to such cooperation.
In Nigeria, Islamist group Boko Haram, another al Qaeda-linked group, has stepped up attacks in recent months after the kidnapping of more than 200 schoolgirls in April sparked international outrage.
The group is suspected in the abduction last week of up to 30 women form nomadic settlements in Nigeria's northeast, close to where it grabbed the schoolgirls, residents and Nigerian media said. The militants were reported to be demanding cattle in exchange for the women.
Along with a desire for international attention, analysts believe the increasingly ferocious attacks are designed to embarrass the Nigerian government and ultimately give Boko Haram more negotiating power in its demand for the introduction of sharia law in northern Nigeria.
Bomb attacks in the capital of Abuja in the run-up to the World Economic Forum in May killed scores of people and illustrated the powerlessness of security forces to stop them.
Ahead of an election next year, President Goodluck Jonathan appears at pains to show his government can tackle Boko Haram, ordering a "full-scale operation" against the group and authorizing security forces to use "any means necessary under the law."
But that's easier said than done, given the difficulties faced by security forces in Africa's most populous nation.
Some analysts say that while Boko Haram's tactics are similar to al Qaeda's, any links are tenuous at best.
"They've got no particular interest in attacking Western targets. It's all focused on their aims: introducing sharia law and a level of autonomy, self-determination for the north," said Martin Roberts, a senior Africa analyst at research firm IHS.
One group that has repeatedly set its sights on American targets is the Yemen-based al Qaeda in the Arabian Peninsula (AQAP), which was believed to have been behind the failed attempt in 2009 to blow up a Detroit-bound airliner by the so-called "underwear bomber."
In a message to the U.S. Congress on Thursday, Obama repeated his administration's warnings that AQAP is "the most active and dangerous affiliate of al Qaeda today."
But the militant splinter groups are evolving so rapidly that - thanks to ISIL's rapid expansion and to operations against AQAP in Yemen - that may no longer be true. (Additional reporting by David Dolan in Abuja and Warren Strobel in Washington.; Writing by Jason Szep and Matt Spetalnick; Editing by David Storey and Lisa Shumaker)