A bomb thrown into a crowded square killed four people in the Egyptian capital Cairo on Sunday, including a French woman and another tourist, officials said.

The explosion, just after dark, struck near the 14th century Khan el-Khalili market in eastern Cairo, where tourists shop for trinkets and sit at outdoor coffee shops.

"We heard a huge sound but we didn't know what it was," a witness told Egyptian state television. "These are just innocent tourists who are not involved in politics coming to visit our country."

Egyptian Health Minister Hatem el-Gabali said a French woman was among the dead and that 17 other people were wounded, including 10 French tourists, one German and three from Saudi Arabia.

Six of the wounded were in a serious condition, security sources said.

Witnesses told security officials that one device exploded after being thrown from a motorbike and bomb disposal experts defused a second device which failed to explode.

Egyptian state news agency MENA, quoting eyewitnesses, said the devices were thrown from the roof of a nearby hotel.

The blast happened as people were congregating around coffee shops in the square to watch a football match on television and coincided with one side scoring a goal, an eyewitness, who did not give his name, told Reuters.

"There was a big noise but at first we thought it could be related to people celebrating," he said. "But then some people running away started screaming and fell on the ground. There was a lot of screaming."

BODIES ON THE GROUND

Egyptian state news television footage showed spots of blood on the paved square as police officers combed the area.

"I was standing in front of my store selling to the tourists and we heard a big explosion," a shop owner told Egyptian state news. "We ran away and when we came back we saw bodies lying on the ground."

Police cordoned off the area and ambulances and police cars with flashing sirens packed into a square near the shops popular with tourists.

Tourism in Egypt, the most populous Arab country, reached record levels last year after a lull in deadly attacks over the last few years. Tourism is one of Egypt's top hard currency earner.

There was no immediate claim of responsibility for the attack although Islamic militants have hit Egypt's tourist industry in recent decades through bomb and shooting attacks.

Abdel-Monem Said, director of the state-funded centre Al-Ahram Centre for Political and Strategic Studies, said the attack did not appear to be the work of a well-organised group.

"They were primitive devices and one didn't work," he said. "The destruction was not large and it seems to be the work of some angry people."

Said said tourism had in the past bounced back quickly from similar incidents.

"Tourism is bad lately because of the international crisis and also because of the Gaza war," he said. "This could add to it but in the past these kind of things haven't had a big effect."

In September last year, masked gunmen seized 19 hostages, including 11 tourists, on a safari in a remote desert area near the Sudanese and Libyan border. All were released unharmed.

Al Qaeda often condemns Egypt's government as a corrupt U.S. puppet and calls for its overthrow. Deputy leader Ayman al-Zawahri said in a message last September that it was among governments "imposed by the Crusader-Zionist campaign (on Islam)".