A British man has been kidnapped in Afghanistan after the convoy he was travelling in was attacked.
The man was with a firm providing security for a road project.
At least three policemen are believed dead after the ambush in the west of the country. The party's interpreter was also reportedly abducted.
The Briton's abandoned vehicle has now been found, and Nato-led troops are using checkpoints and a surveillance aircraft in their search for the men.
There is confusion over who was responsible, with the Taleban blamed by police and security officials while a government spokesman initially blamed criminals.
Taleban spokesman Abdul Latif Hakimi told the Pakistan-based Afghan Islamic Press that they were behind the attack.
The BBC's Andrew North said suspicion was likely to fall on the Taleban but that this was not an area where they have been active.
Afghan security forces believe the British man was taken towards a mountainous area in Farah province.
He was in a convoy of vehicles with armed guards from the American company US Protection and Investigation, which is helping protect the project to build a major road from the southern city of Kandahar to the western city of Herat.
They were accompanied by Afghan police escorts and were heading to their heavily fortified camp nearby, according to others in the convoy, when three cars drove past at speed.
One pulled over and its occupants then opened fire. Guards in the British man's convoy returned fire but the other two cars blocked the road.
At least one vehicle managed to escape but as those inside looked back they saw armed men forcing the British man and his Afghan colleague to drive their vehicle away.
The Nato-led peacekeeping force in Afghanistan said it had established checkpoints in the area and had mobilised a surveillance aircraft, the Reuters news agency reported.
The British Embassy in Kabul confirmed there had been an incident and that it was working with the Afghanistan government.
A Foreign Office spokeswoman said: "We are aware an incident has taken place in Afghanistan as a result of which a UK national is missing and we are urgently seeking further details from the Afghan authorities."
Violence has been increasing in Afghanistan in the run-up to parliamentary elections due next month.
The kidnapping comes just weeks after the abduction of a Lebanese engineer who was involved in the construction of another road in southern Afghanistan.
The man was released unhurt a few days later.
Insurgents have stepped up attacks in the lead-up to elections on 18 September.
More than 1,100 people have been killed in the last six months.