Security forces in Yemen have surrounded a group of tribesmen believed responsible for the kidnapping of two French tourists.

The unnamed couple and two Yemeni guides were snatched from their car in Amran province, about 60km (37 miles) north of the capital, Sana'a, on Monday morning.

A police source had earlier told the French news agency AFP that the victims had been taken to the remote Jawf region, further north, but gave no further details.

A Yemeni official said large numbers of security forces had been deployed in the area. He added that tribal leaders in the region who were related to the kidnappers had tried to begin negotiations.

The French foreign ministry said its embassy was in contact with Yemeni authorities.

A spokesman said citizens had been reminded to "exercise the greatest caution in Yemen" and to stay away from the area around Jawf, which is considered too risky for tourists.

The deputy-governor of Amran, Abdul Salam Atif, said the authorities were awaiting the kidnappers' demands, but insisted the couple were not in danger.

"They will be treated as guests now, even though we do not allow this, we condemn it as criminal," he said, adding that he did not believe an Islamic group was responsible.

Mr Atif said he believed the kidnapping was aimed at the Yemeni Government, not the West.

Death penalty

Tourists and foreigners working in Yemen are often seized by disgruntled tribesmen trying to press the government for better infrastructure in remote areas of the country or the release of imprisoned tribe members.

Most hostages have been released unharmed, but in 1998 four Westerners were killed when Yemeni security forces stormed a hideout where kidnappers were holding 16 hostages.

Nobody had been kidnapped since three Americans were held by armed tribesmen for three days last October.

Yemen has recently set up special courts to try kidnappers and introduced the death penalty for the offence.

In November, Yemeni President Ali Abdullah Saleh formed a special forces unit to combat "terrorism", including the kidnapping of foreigners.