Gunmen have kidnapped two Chinese engineers and four Afghans in northern Faryab province, a local police official said on Sunday.

Sayed Aslam Ziarati, police chief of Qaisar district where the men were abducted on Saturday evening, said they had been working on a road project in the area with a Chinese company.

"They were travelling in two vehicles, when gunmen seized them. We don't know who the gunmen are," Ziarati said. He added that two of the Afghans were also engineers.

The Afghan Islamic Press news agency said they had been kidnapped by the Taliban, quoting a spokesman for the insurgents.

Reuters could not immediately reach the Taliban for comment.

The Taliban often stage kidnappings as part of their campaign against coalition forces but abductions have also become a lucrative business for criminal gangs and rival tribes.

Northern Afghanistan has long been seen as relatively safe but violence is at its highest levels since the ouster of the Taliban government in 2001, and the insurgency is spreading to previously calm parts of the country.

Taliban fighters in October attacked a police post in Faryab and took away eight officials.

Last year was the bloodiest of the war for both civilians and foreign troops, and the United States is sending 30,000 more troops to try and turn the tide.

Other NATO countries are sending around 7,000 more. There are some 110,000 foreign troops in Afghanistan, including 68,000 Americans.