PESHAWAR, Pakistan - Pakistani soldiers are closing in on the main town in the Taliban bastion of Swat, the army said on Saturday, in an offensive that has driven more than a million people from their homes.

The army launched the offensive more than a week ago to stop the spread of Taliban influence after the collapse of a peace pact the United States had criticized as tantamount to abdicating to the militants.

Militant violence in nuclear-armed Pakistan has surged over the past two years, raising fears for its stability and alarming the United States, which needs Pakistani action to help defeat al Qaeda and bring stability to neighboring Afghanistan.

Earlier, a car packed with mortar bombs blew up in the city of Peshawar, killing 11 people. A suspected U.S. drone aircraft fired missiles at militants in another region near the Afghan border, killing 28 of them, government officials said.

The offensive in the one-time tourist valley of Swat, northwest of Islamabad, has forced at least 1.17 million people from their homes, the U.N. refugee agency said, adding the world needed to respond massively.

A military spokesman said clashes had erupted in different parts of Swat and 47 militants had been killed in the past 24 hours. That would take the toll in the offensive to about 970 militants and 48 soldiers, according to the military.

Reporters have left Swat and there was no independent confirmation of the casualties. About 15,000 members of the security forces face about 5,000 militants, the military says.

The security forces are closing in from different directions and have been able to inflict many more casualties, military spokesman Major-General Athar Abbas told a briefing.

Security forces are getting close to Mingora city. The aim is to isolate and block the movement of fleeing terrorists.

The Taliban hold Mingora, Swat's main town, and many civilians are believed to be still there.

FLOOD OF PEOPLE

Most political parties and members of the public support the offensive, despite skepticism about an alliance with the United States in its campaign against militancy.

But opposition will grow if many civilians are killed or if the displaced are seen to be enduring undue hardship.

U.N. High Commissioner for Refugees Antonio Guterres said the flood of people from Swat this month was one of the most dramatic displacement crises in the world in recent times.

The United Nations has registered 1.17 people though many are believed not to have bothered to register. They are joining about 565,000 displaced by earlier fighting in the northwest.

A failure to respond could generate instability so it was in the world's interest to help, Guterres told a news conference.

This is the moment in which massive support is required ... This is not the moment for symbolic gestures, he said.

Among the dead in the Peshawar blast were four children passing in a school bus, police said. Peshawar is the main city in northwestern Pakistan, to the southwest of Swat.

There was no claim of responsibility but officials have warned of the danger of bombs in response to the Swat offensive.

DRONE STRIKE

Earlier, the suspected U.S. drone aircraft fired missiles at militants in the North Waziristan ethnic Pashtun tribal region, on the Afghan border to the southwest of Peshawar.

Pakistani intelligence agents said the militants were preparing to cross into Afghanistan to fight there and among the 28 dead were two Arabs. Their identities were not known.

The United States, alarmed by deteriorating security in Afghanistan, stepped up drone air attacks on Taliban and al Qaeda militants in Pakistan last year, despite Pakistani objections.

Pakistan says the drones violate its sovereignty and undermine efforts to deal with militancy because they inflame public anger and bolster militant support.

U.S. officials say the missile strikes are carried out under an agreement with Islamabad that allows Pakistan's political leaders to decry the attacks in public. Pakistan denies that.

The spread of Taliban influence and worsening security have raised the doomsday scenario of militants allied to al Qaeda gaining control of Pakistan's nuclear weapons.

But Prime Minister Yusuf Raza Gilani dismissed such fears, saying detractors were spreading disinformation about the security of the weapons to undermine the country.

The weapons were the cornerstone of Pakistan's policy of deterrence and it would retain them under fail-safe security at all costs, he said.

No amount of coercion, direct or indirect, will ever force Pakistan to compromise on its core security interest, he said.

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