Pakistani police Wednesday refused American diplomats to go out of the port city of Karachi without proper travel documents, local media reported.

Four vehicles of U.S. consulate in Karachi and two French consulate vehicles were heading to interior parts of southern Sindh province, whose capital is Karachi, when they were stopped by the police and members of the security agencies at a Toll Plaza for routine check.

The U.S. nationals in one vehicle did not have permission to travel and were sent back to Karachi, Geo television reported.

Diplomats and their Pakistani guards in three other vehicles and two French consulate vehicles were allowed to proceed as they had the required travel documents.

Pakistani government has made it compulsory for diplomats and foreign nationals to get special permission for travelling out of main cities after a undercover CIA agent was arrested in the eastern city of Lahore in February for killing tow Pakistani nationals.

Raymond Davis was freed after families of the slain men reached a blood-money agreement with him.

On July 20, the police stopped seven U.S. embassy officials from going to northwestern city of Peshawar when their travel documents were not found to be in order.