"Four vehicles are said to have been stopped ... close to the South Waziristan border," he said.

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"The four buses were stopped, allegedly by the Taliban and the political administration has proceeded to the area to negotiate with them and get those vehicles moving. 

"We have to be careful to see whether this is an abduction or whether those four vehicles have been detained."

The Associated Press news agency quoted a local police official as saying the staff and students had left the college after being warned that it could be attacked.

There was no immediate comment on the incident from the Taliban, whose fighters are also battling the Pakistani military in Swat, a district in the adjoining North West Frontier Province (NWFP).

Curfews lifted

Officials lifted the curfews in the towns of Bahrain, Madyan, Fatehpur, Khwazakhela, Matta and Alpurai and in the district of Shangla in the Swat valley on Monday.

The move allowed thousands of people trapped amid the army's campaign against Taliban fighters to search for food and supplies.

The military has said it is pushing the Taliban back after it regained control of Mingora, the main city in Swat, following weeks of fighting.

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 Witness: Pakistan in crisis

However, there are fears that military successes will lead to retaliatory Taliban attacks in other areas.

At least two people were killed and 18 others wounded when a blast struck a bus stop in Kohat on Monday.

Kohat is an important garrison town in NWFP.

Ehsanullah Khan, a senior police official, said that the explosive device was hidden in a sack and confirmed it was detonated by remote control.

Pakistan has stepped up security in its cities following recent suicide bombings away from Swat, including one in Lahore, in the eastern province of Punjab, that killed about 30 people.

Analysts say that the authorities must rapidly restore basic services to stop the Taliban from exploiting frustrations and poverty to remount its campaign.

Sebastian Brack, a spokesman for the International Committee of the Red Cross, told Al Jazeera that those who remained in the valley, as well as the hundreds of thousands of refugees, faced numerous problems.

"There are huge problems in terms of basic services that need to be provided - electricity, water, phone lines, the re-establishment of family links," he said.
"The second level of the humanitarian problem is all those people who found refuge in host families, which are fairly close to the area where the fighting is taking place but which are not receiving the bulk of the humanitarian relief effort.
"That effort is being concentrated further south at the IDP [internally displaced persons] camps."

The Pakistani army launched its offensive against Taliban fighters in Swat and surrounding districts a month ago after they violated the terms of a ceasefire.