Sana'a: Spanish, French and US tourists once filled the winding alleys of Sana'a's old quarter, drawn by Yemen's 2,500-year-old history and unique architecture.

But a spate of attacks on foreigners is driving visitors away and souvenir shop owner Hussain Abdul Moghni says the only tourists who come to Yemen these days are "adventurers".

"We had more than 3,000 tourists in the old city before, but they fell to 600 after the attack on the Spanish tourists," said Abdul Moghni, referring to a July 2007 explosion which killed seven Spanish nationals.

Now, since shells were fired this month at a residential complex housing Americans and other Westerners, there have been no more than half a dozen tourists, he added.

"The tourists who are here now are the adventurers. Being here is a matter of life or death," he said.

Al Qaida claimed responsibility for the attack on the residential compound - in which no one was hurt - and for a mortar attack that missed the US embassy last month but wounded 13 girls at a nearby school.

A blast also shook an area near the offices of a Canadian oil company on Thursday.

In January, gunmen ambushed two tourist vehicles in Shibam and killed two Belgian women.

The seven Spanish tourists were killed in a blast at the Queen of Sheba temple in the volatile eastern province of Marib.

One of the poorest countries outside Africa, Yemen has been trying to encourage tourism and draw foreign visitors to ancient sites such as the Biblical-era temple and the 16th century towers of Shibam, dubbed the "Manhattan of the desert".

But despite its wealth of attractions, from cool mountains, to Red Sea and Arabian Sea coasts, wild valleys and ancient ruins, tourism accounts for only 1.5 per cent to 2 per cent of Yemen's GDP.

The Tourism Ministry, set up only in 2006, faces an uphill task to fulfil its target of attracting one million tourists by 2010.

"Five German tourists who were supposed to arrive this week, cancelled their booking after the attack... Every time there is an attack, tourist numbers decrease," says Abdul Wahid Al Hemiaree, manager of a 22-room hotel in Sanaa.

"What we are seeing now is a war on the economy ... by these attackers," Abdul Moghni said.

"Tourists are now afraid to come to Yemen, especially the Americans because they are concerned they are being targeted," he said.