The route was closed on Tuesday when Pakistani forces began an operation against militants in the area, which is still continuing.

The leading administrator in Khyber told the BBC all transport along the route was operating during the day.

There has been a spate of hijackings and attacks on vehicles in the area.

The Khyber Pass is the most important of the two routes from the Pakistani port of Karachi used by international forces to deliver supplies.

Arrests

Khyber tribal district administrator Tariq Hayat said the Khyber Pass was reopened on Friday morning for lorries "carrying trading goods to Afghanistan as well as Nato supplies".

Mr Hayat said the route would be open each day from 1100 to 1600, and there were no security convoys travelling with the lorries.

Witnesses said more than 200 trucks carrying goods and Nato supplies to Afghanistan had crossed the Torkham border point, which had also been closed for the operation, during Friday's curfew break.

Mr Hayat said he hoped the situation would "return to normal in one or two days".

Troops met little resistance from militants who fled to the neighbouring Mohmand region, reports say.

More than 40 people were arrested and suspected militant houses and camps destroyed in the offensive, officials said.

The offensive involves ground troops, helicopters and tanks in the Jamrud sub-district.

Dangerous route

The section of the Khyber Pass that passes through Jamrud is the most insecure stretch of the road.

The international forces in Afghanistan praised the Pakistani offensive despite the fact that the route carries about 75% of their supplies via Karachi.

Since September the Taleban in Pakistan have targeted vehicles carrying supplies for foreign forces in Afghanistan.

They have hijacked lorries, stolen their cargo and kidnapped their drivers.

Some lorry drivers recently suspended organised convoys to Afghanistan because of the worsening security although some supplies did continue under heavy paramilitary guard.