* Army says kills 27 militants in air strikes
* Troops cordone off region, curfew imposed
* Five Pakistan troops killed by roadside bomb
* About 10,000 refugees flee to Afghanistan (Adds army statement, IED attack, Khost refugees)
By Haji Mujtaba
MIRANSHAH, Pakistan, June 16 (Reuters) - Pakistani fighter jets pounded North Waziristan on Monday, a day after the army announced the start of a full-scale military operation to flush Islamist insurgents out of the volatile region bordering Afghanistan.
In a long-awaited military operation precipitated by a deadly insurgent attack on Pakistan's biggest airport a week ago, Pakistan has deployed troops, artillery and helicopter gunships to fight insurgents in North Waziristan.
The Taliban and their ethnic Uzbek allies holed up in North Waziristan have both claimed responsibility for the June 8 commando-style attack on Karachi airport, which was seen as a strategic turning point in how Pakistan tackles the insurgency.
The army said combat aircraft destroyed six hideouts in the Shawal sector of North Waziristan, home to some of Pakistan's most feared militants and al Qaeda commanders, early on Monday.
"In these precise strikes 27 terrorists were killed. There is no (civilian) population in the area," it said in a statement.
"(The) operation in North Waziristan Agency is progressing as per plan. ... North Waziristan Agency has been isolated by deploying troops along its border with neighbouring agencies and FATA (Federally Administrative Tribal Areas) regions to block any move of terrorists in and out of the Agency."
It said troops had cordoned off all militant bases, including the town of Mirali where many ethnic Uzbek and other foreign fighters are based, and the regional capital of Miranshah.
The Taliban appear determined to fight back. In the first attack since the start of the operation, at least five Pakistani soldiers were killed on Monday when a roadside bomb hit an army convoy just north of Miranshah.
"It was an improvised explosive device," said an intelligence official.
The all-night attack on Karachi airport all but destroyed prospects for peace talks with the Taliban militants, who are fighting to topple the government and impose a strict Sharia-based theocracy in the nuclear-armed nation.
Public opinion appears to have swung in favour of a military operation after the Karachi attack, even though such a response in North Waziristan means a higher risk of revenge attacks by the Taliban outside the tribal region.
"Operation at last!" The Nation daily said in a front-page headline.
Prime Minister Nawaz Sharif has long insisted that he could bring insurgents to the negotiating table but the start of the offensive is seen as a victory for hawks in the army who have long called for tough military action.
The United States, in the process of withdrawing troops from neighbouring Afghanistan, also wants Pakistan to do more to crush the insurgency and eliminate al Qaeda hideouts tucked away in the remote mountains straddling the frontier.
OPERATION "PROPHET'S SWORD"
The army imposed an all-day curfew in North Waziristan as the operation got under way and turned off mobile phone services to undermine the insurgency and restrict people's movements.
Independent confirmation of the events or other details were not available immediately from a region where journalists are not allowed to operate freely.
Expecting an escalation of violence, two-thirds of families have fled from the ethnic Pashtun region, residents said, many heading for the Gorbaz district of Afghanistan's Khost province.
Mohammad Akbar Zadran, Gorbaz district chief, told Reuters nearly a thousand families, or around 10,000 people, have now entered into Gorbaz district, and the number was growing.
"We have packed up everything and are ready to leave as soon as the curfew is lifted," said Ethasham Khan, a resident of Miranshah, where the usually bustling streets were empty.
The curfew will be relaxed in the next couple of days to allow residents to leave the area, a security official said.
Tellingly, the Pakistani military's operation against the Islamist militants in North Waziristan is called Zarb-e-Azb in Urdu, or "Strike of the Prophet's Sword".
For now, ground troops - numbering some 80,000 in North Waziristan, according to military sources - have not been involved in direct military action, leaving F-16 combat jets to lead the offensive with air strikes.
It was also unclear how long officials expect the operation to last in a region of forbidding mountainous terrain that has never been subdued by any government.
Separately on Monday, Omar Jillani, an intelligence official who police said is the nephew of Pakistan's powerful chief justice, was kidnapped in the eastern city of Multan by suspected Taliban gunmen, police said.
Security is visibly tighter in the capital, Islamabad, as well, with street patrols by paramilitary Rangers and police. In Lahore, the cultural capital, police have added checkpoints.
Islamabad's central Kohsar market, a shopping and dining spot for foreigners and rich Pakistanis, was largely deserted as the operation got underway on Sunday afternoon.
The Pakistani Taliban are allied with Afghan insurgents of the same name but operate as a separate entity, uniting dozens of smaller jihadist groups based in the tribal areas. (Additional reporting by Asim Tanveer in MULTAN, Elyas Wahdat in KHOST, Hamid Shalizi in KABUL; Writing by Maria Golovnina; Editing by Jeremy Laurence)