The historic district was the scene of a previous bomb attack in 2005

One person has been killed and about 19 people, mostly foreigners, injured in a bomb blast outside Egypt's historic Hussein mosque in Cairo.

Police said the person killed in the explosion on Sunday in the popular tourist area was a French woman.

Passersby were injured after being hit by stone and marble fragments after the bomb went off outside the mosque, a police official at the scene said.

French and German nationals were among the wounded.

"It was an explosive, perhaps a hand grenade," one police official said.

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

Blood stains could be seen in the front courtyard of the mosque, next to the famed Khan el-Khalili bazaar.

Police detonated a second device without causing any injuries.

Blast investigated

Riot police cordoned off the area and sniffer dogs could be seen as worshippers were being evacuated from the mosque.

"I was praying and there was a big boom and people started panicking and rushing out of the mosque, then police came and sealed the main door, evacuating us out of the back," said Mohammed Abdel Azim, who was inside

the mosque at the time.

It was not clear who was behind the attack or if tourists had been deliberately targeted.

"Investigations are at a preliminary stage at the moment," Amr el-Kahky, Al Jazeera's correspondent in Cairo, said.

"It is very difficult to speculate whether foreigners were the target of this attack.

"All the Islamic groups that were operating and were violent in the nineties [in Egypt] have issued an initiative in which they declared a unilateral ceasefire against the Egyptian government."

The historic district was the scene of a previous bomb attack in 2005 in which two tourists were killed and 18 wounded.