Pakistan suspended the vehicles from the passageway for a security review last week afterwhose load included Humvees bound for the U.S.-led coalition.
On Monday, a dozen or so paramilitary pickups joined a convoy of around 30 vehicles as part of new security measures. The escort trucks bore rocket-propelled grenades and heavy machine guns. Earlier, the transport trucks traveled with little or no security.
Al Qaeda and Taliban fighters, as well as ordinary criminals, are behind escalating violence along the porous Afghan-Pakistan border. The danger has made the Khyber Pass an increasingly perilous 30-mile stretch, but one that the U.S. and NATO still rely upon heavily.
The violence in the region continued Monday when an Afghan official said a suicide bomber blew himself up at the entrance of a government office in Kandahar province, killing two policemen and a civilian.
Across the border in Pakistan, a suicide car bomber attacked an army post in the northwest on Monday, killing at least three people, while violence elsewhere in the region left at least five suspected militants dead.
Pakistan is engaged in a pair of major offensives against militants who use pockets of the northwest to stage attacks on American and NATO forces in Afghanistan. Insurgents have retaliated over the offensives by staging a wave of attacks throughout Pakistan.
The suicide attack Monday happened in Gashkor, a village in the Swat Valley, said police official Ali Rehman. Swat, a former tourist destination, is the scene of one of the two offensives.
The other offensive is focused on Bajur, a tribal region bordering Afghanistan that is a rumored hiding place of al Qaeda leader Osama bin Laden.
Security forces used artillery fire to kill at least five suspected insurgents in parts of Bajur overnight, said Jamil Khan, a No. 2 government representative in the area. The military claims to have killed 1,600 insurgents in Bajur since August.
It was not possible to confirm exactly what was being transported in Monday's convoy through the Khyber Pass. Military supplies usually travel in sealed, unmarked containers. The route is also a critical commercial trade passage between the two countries.
A U.S. military spokesman in Afghanistan insisted Monday the suspension had not affected operations there. "We continue to move supplies through Pakistan to Afghanistan," said Lt. Cmdr. Walter Matthews. "I can't give you the route."
Bakhtiar Khan, a No. 2 government representative in the area, said troops were authorized to shoot "at sight" any militants or otherwise armed attackers who attempt to assault the convoy.
Akhtar Gul was among the drivers who had been waiting for several days to enter the pass. He was pleased to see the armed escorts.
"Previously we had many apprehensions about the security of our lives and the trucks," said Gul, who said he did not know what was in the sealed container he was transporting. "But we hope that now it will be safe."
U.S. and NATO officials in Afghanistan have sought to play down threats posed to the convoys coming through Pakistan, but NATO has said it is close to striking pacts with Central Asian countries that would let it transport "non-lethal" supplies from north of Afghanistan.
In April, NATO concluded a transit agreement with Russia, but it will be of practical use only once the Central Asian nations between Russia and Afghanistan come on board.
Most of the supplies headed to foreign troops in Afghanistan arrive in the southern Pakistani port city of Karachi in unmarked, sealed shipping containers and are loaded onto trucks for the journey either to the border town of Chaman or through the Khyber Pass.