Peshawar - Pakistani police prevented activists who were protesting US drone strikes from blocking trucks carrying Nato troop supplies to and from neighbouring Afghanistan on Monday.
The intervention was the latest chapter in a saga that began on Saturday, when thousands of protesters led by Pakistani politician and cricket star Imran Khan blocked a road in northwestern Khyber Pakhtunkhwa province, which is used to ship goods to and from Afghanistan.
Khan's party, Pakistan Tehreek-e-Insaf, said they would block Nato shipments until the US ended drone attacks.
On Sunday, members of Khan's party stopped trucks and roughed up drivers ferrying Nato supplies at a toll booth on the outskirts of Peshawar, Khyber Pakhtunkhwa's provincial capital.
Police were present at the scene on Sunday but did not stop the protesters, some of whom were carrying wooden batons.
Police officer Behram Khan said on Monday that police would permit peaceful protests on the roadside, but activists would not be allowed to stop trucks as they did before.
Police also opened an investigation into the activists' actions that could lead to legal charges, he said.
Covert CIA drone strikes targeting Islamic militants in Pakistan's northwest have long been a sensitive subject, with officials regularly criticising them in public as a violation of the country's sovereignty.
The issue is more complicated, however, since the government is known to have supported at least some of the attacks in the past.
Imran Khan, whose party runs the Khyber Pakhtunkhwa government, has been a vocal critic of the strikes. The route blocked by his activists leads to one of two crossings used by trucks to carry Nato troop supplies and equipment to and from Afghanistan.
The other crossing is in southwest Baluchistan province and has not been affected by the protest.
The federal government has also criticised drone strikes but has indicated it has no interest in blocking the Nato supply route, which could spark a crisis with the US and other Nato countries.
The police actions on Monday indicated that the federal government had intervened to stop the Nato blockade.