* Five dead after roadside bomb hits
* Taliban spokesman says more attacks likely
* Navy-run institutions closed for precaution (Adds Taliban claim, security official's quotes)
By Faisal Aziz
KARACHI, April 28 (Reuters) - Taliban militants detonated a roadside bomb in the Pakistani city of Karachi on Thursday, killing four members of the navy, the third attack on the navy in less than a week.
A motorcyclist was also killed in the blast targeted at a navy bus, while at least five people were wounded, navy spokesman Commander Salman Ali and a hospital official said.
Security experts say the attacks on the navy, seen as a soft target with less effective protection, could be part of a new strategy to widen their violent campaign.
Militants linked to al Qaeda and Taliban have carried out several attacks on the Pakistani army and air force, which spearhead offensives against them in their northwestern strongholds near the Afghan border, but the navy had not been targeted before this week's attacks.
The Taliban claimed responsibility for the attack, as they did for the twin attacks in Karachi on Tuesday, when two bombs hit buses carrying navy personnel, killing four people and wounding 56. [ID:nL3E7FQ09V]
"Our men carried out this attack and all security forces are our target," Ehsanullah Ehsan, a Taliban spokesman, told Reuters by phone from an undisclosed location.
"They will be attacked everywhere in the country. Our organisation is still strong in cities of Pakistan."
NAVY-RUN INSTITUTIONS CLOSED
A senior security official said educational institutions run by the Pakistan Navy in Karachi were closed for three days after Tuesday's attacks.
Karachi is Pakistan's biggest city and commercial hub. It is also home to the main base of the Pakistani navy.
"It is a precautionary measure as the militants are targeting navy buses, many of which are used to pick and drop school children," the official said, who declined to be identified. "We may have to extend the closure further given the situation."
Some security experts said the insurgents were after all security forces, not just the navy, and this week's attacks on the navy could mean they were widening their targets, with more dangerous devises.
"It's not the navy that is being targeted, it is the armed forces," said former interior minister and retired army general Moinuddin Haider.
"And the most dangerous thing is that IEDs (improvised explosive devices) and remote bombs are now being used. This is a new thing which here first started in Iraq and has caused a lot of damage in Afghanistan," said Haider.
The attacks come days after Pakistan army chief General Ashfaq Kayani said his forces had broken the back of militants. [ID:nL3E7FN01Z]
Senior police officer Tahir Navaid said that Thursday's attack took place on one of Karachi's busiest roads. A civilian car and motorcycle were also damaged in the explosion, he said.
The insurgents have waged a campaign of bomb and suicide attacks across the country in retaliation for military offensives against them.
In 2002, 11 French engineers and technicians working on the construction of submarines for the Pakistan navy were killed along with three Pakistanis in a suicide bombing outside a hotel in Karachi. (Additional reporting by Imtiaz Shah in Karachi and Saud Mehsud in Dera Ismail Khan; Editing by Zeeshan Haider and Yoko Nishikawa)
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