Cairo -- Egyptian security services believe a tiny Islamist cell carried out a nail-bomb attack near a popular tourist site in Cairo that killed a French teenager, a government newspaper said on Tuesday.

The investigation into Sunday's bombing near the famed 14th century Khan al-Khalili bazaar is focusing on an isolated group of three or four Islamists, Al-Ahram newspaper reported.

Police said they arrested three suspects and were questioning another 15 but as yet no one has claimed the attack, the first targeting Westerners in Egypt since 2006 and casting a shadow over the country's vital tourism industry.

Al-Ahram said the homemade bomb weighed up to 1.5 kilograms (more than three pounds), contained nails and metal fragments and an explosive material similar to the kind used in fireworks.

A timer was used to detonate the device, which had been placed on a marble bench, the newspaper said, contradicting witness statements that it had been thrown from a rooftop. Another bomb was found nearby but was defused by police.

A 17-year-old French girl was killed and 24 other people, mostly French tourists, and also including three Saudis, three Egyptians and a German, were injured in the blast.

The French wounded flew home on Tuesday with their relatives and the body of the dead girl is to be repatriated later in the day after her family arrived on Monday, airport and French consular sources said.

"This act highlights social and political unease but appears to be the work of an individual or a group acting in isolation," said Amr Shubaki, a researcher at the Al-Ahram centre of strategic studies.

"The people who did this, perhaps a group of Islamists working on their own, were not going for French people but their target was clearly foreign tourists," Dhia Rashwan, an expert on radical Islam, told AFP.

However, General Fuad Allam, former head of the state security service, warned the attack could herald "a new wave of terrorism in Egypt," spurred by the global financial crisis and the region's problems.

It was the first deadly attack on tourists in Cairo since a bombing in the same neighbourhood killed two tourists and wounded 18 in 2005.

"That was a small Islamist cell and Sunday's attack seems similar in the choice of place and the very basic operating method," said Rashwan, who works for the Al-Ahram strategic studies centre.

A series of bombings from 2004 to 2006 killed a total of 120 people in major Red Sea resorts on the Sinai peninsula that were blamed on militants loyal to Al-Qaeda.

The United States strongly condemned the attack in Egypt, one of its closest allies in the Middle East and the region's second largest recipient of US aid after Israel.

"We will continue to work closely with the government of Egypt to do what we can to support them in their efforts to fight terrorism," said State Department spokesman Robert Wood.

African Union president Jean Ping also denounced the "blind violence" of the attack.

Last year, 13 million tourists visited Egypt, bringing in 11 billion dollars.

Egypt has been afflicted by violence throughout its modern history. President Anwar Sadat was assassinated by Islamists in 1981 and his successor Hosni Mubarak has been the target of a dozen attacks in 28 years in power.

The country lives under a state of emergency, allowing arbitrary detention, which has been repeatedly renewed pending finalisation of an anti-terror law.

AFP/Expatica