Kabul: Afghan police arrested two British private security contractors and two Afghan colleagues and ordered their company closed down after finding a cache of weapons in their vehicle, an official said yesterday. They are being held for investigation into illegal arms transport.

Their detention spells the latest trouble for Afghanistan's dozens of private security companies that guard supply convoys, development projects and private businesses. President Hamid Karzai has ordered all the protection companies to shut down by March and to be replaced by a unified government-run protection force.

Police who stopped the contractors' vehicle at a Kabul checkpoint on Tuesday found more than two dozen AK-47 rifles in a metal box covered by a blanket, Ministry of Interior spokesman Sediq Seddiqi told a press briefing.

All 30 weapons had their serial numbers scratched off, and the men had no permits for them, so police arrested all four men on suspicion of illegal arms transport, Seddiqi said. He said the case has been sent to Afghanistan's attorney general for investigation.

Authorities ordered the immediate shutdown of Afghanistan operations of their company, the international security consulting firm GardaWorld, and are questioning other company employees.

"They have to pay all the dues they owe to the government of Afghanistan, and they cannot operate any more after that," Seddiqi said. GardaWorld had no immediate comment yesterday. The security firm specialises in high-risk areas around the world, with offices in Iraq, Pakistan, Yemen and Haiti.