PESHAWAR, Pakistan (Reuters) -- A suicide car-bomber has killed 10 people at a security checkpost in northwest Pakistan as the army battled Taliban militants in the Swat Valley.
The offensive in Swat, 130 kilometers northwest of Islamabad, is seen as test of the government's resolve to get to grips with an intensifying Taliban insurgency and comes after the United States accused it of "abdicating" to the militants.
The fighting has sparked a civilian exodus from the former tourist valley, raising fears of a humanitarian crisis.
About 200,000 people have left their homes in recent days and in all about 500,000 are expected to flee. They join 555,000 people displaced earlier from Swat and other areas because of fighting since August.
The bomber killed two paramilitary soldiers and eight civilians when he set off his explosives in a queue of cars at a checkpost on the outskirts of the main northwestern city of Peshawar, said a police spokesman, Fazal Naeem.
"The target was the checkpost but he couldn't manage to reach the soldiers because of the queue," Naeem said.
There was no claim of responsibility for the blast but militants have unleashed a series of bomb attacks over the past two years, many aimed at ending security force operations against them.
The army launched a full-scale offensive in Swat, about 110 kilometers northeast of Peshawar, on May 7 after the government ordered troops to eliminate militants.
The military said on May 10 that up to 200 militants had been killed in Swat and the neighboring Shangla district in the previous 24 hours. The figure could not be independently confirmed.
Aircraft attacked militant positions in the valley on May 11, while a curfew kept frightened civilians huddled in their homes, residents said by telephone.
The army lifted the curfew for nine hours on May 10 to enable people to flee.
The offensive was launched while President Asif Ali Zardari, the widower of former Prime Minister Benazir Bhutto, was in Washington assuring a nervous United States that his government was not about to collapse and was committed to fighting militancy.
Action by nuclear-armed Pakistan against militants in its northwest is vital for U.S. efforts to defeat Al-Qaeda and stabilize Afghanistan.
Most political parties and many members of the public support the offensive but that could change if the civilians displaced in the country's larget-ever internal migration are seen to be suffering unduly or if many civilians are killed in the fighting.
Opposition leader and former Prime Minister Nawaz Sharif, who has sounded supportive of government action against the militants, visited a camp for the displaced on May 11 and said it was everybody's responsibility to help.
"It's a very unfortunate situation," Sharif told reporters.
"The nation in no way approves the activities of those elements who are responsible for the displacement and migration of these people," he said.