A British engineer and his Afghan interpreter were kidnapped when gunmen attacked a convoy in western Afghanistan and killed three police escorts, the Interior Ministry said on Thursday.
Taleban guerrillas said they carried out attack on Wednesday in the western province of Farah and were holding the Briton, but Interior Ministry spokesman Lutfullah Mashal said criminals were responsible, although they might be working for the Taleban.
"They killed three policemen and kidnapped a British engineer working for a road construction company," Mashal said.
The attack took place on the road between the south-western city of Kandahar and the western city of Herat, he said.
One of the attackers had been captured but the rest, driving in three vehicles, had escaped into mountains, he said. Later, another of the gunmen's vehicles was found abandoned, he said.
"Police are chasing them ... right now we are focusing on the safe release of the international employee," he said.
He declined to identify the British man or the company he was working for but said he was a civilian. No demands had been made for the man's release, he said.
The British embassy in Kabul was aware of an incident in the west of the country, as a result of which a British national was missing, an embassy spokeswoman said.
"We are urgently seeking details from the Afghan authorities," she said, adding that next of kin of the missing man had asked that his name not be released.
Mashal said the area where the attack took place was infested with robbers and the kidnappers too were criminals, not militants, although they might be in league with the Taleban.
"Since the Taleban are having a big problem recruiting people they hire criminal gangs. This gang might be hired by them," he said.
Taleban guerrillas, who have not been known to operate in force in the west, are battling about 20,000 US troops in the south and east. About 10,000 Nato-led peacekeepers operate mostly in Kabul, the north and the west.
About 1,000 people, including 48 US troops, have been killed in a surge of violence this year, but Afghan and US officials say September 18 elections will not be disrupted.
Taleban spokesman Abdul Latif Hakimi said the group's guerrillas had carried out the attack. The British man's fate would be determined by a Taleban council, or shura, he said.
"The supreme shura will decide on demands and his fate," Hakimi said by telephone from an undisclosed location.
He said the British man, whom he identified as David, had suffered a slight bullet wound to a hand but he had been treated and he was fine.
A spokesman for Afghanistan's Nato-led peacekeeping force, which has units in the west, said checkpoints had been set up and surveillance aircraft scrambled late on Wednesday.
Some US forces are stationed at an air base not far from the location of the attack but the US military had not been involved in the incident, a spokeswoman said.
Nearly four years after the Taleban were forced from power by US-led forces, security remains a major problem in Afghanistan.
Suspected Taleban members have kidnapped several Turkish and Indian nationals working on road projects in the south, but have released them unharmed after ransoms were paid. A Lebanese engineer kidnapped by the Taleban last month was freed unharmed.
Gunmen kidnapped an Italian aid worker in Kabul in May. She was released unharmed after more than three weeks in captivity. Her captors were members of a criminal gang, the government said.
A British aid worker was shot dead in Kabul in March. That crime has not been solved.