The blast occurred in old Cairo in an area popular with tourists

The man, who died in the blast, has not been named. Police said he came from an impoverished area just north of Cairo.

They have also arrested three others on suspicion of being accomplices.

Thursday's nail-bomb attack in a part of Cairo popular with tourists is the first in the capital for seven years.

The BBC's Heba Saleh reports from the capital that officials there are keen to portray the act as exceptional.

Our correspondent says they are aware of the need to limit any damage to tourism, which is one of Egypt's main sources of income.

Militants condemn

Tourists from France and the US were killed and at least 17 others injured in the market blast in the historic heart of Cairo.

Investigators are quoted as saying that initial inquiries suggest the four suspects had no links with any militant groups.

Earlier police said the bomber used a crude homemade explosive device which was packed with nails.

A previously unknown Islamic group has said it was behind the blast.

But al-Gamaa al-Islamiya - the group used to target tourists in the 1990s which has since renounced violence - condemned the attack.

Islamic militants in the country have staged attacks on tourist attractions in the past.

In the most recent attack in October, 34 people died, including several Israelis, when militants bombed several hotels in the Sinai peninsula.

The government accused a group of Sinai residents, some of whom were killed in the attacks. Very little information has come out about them, though their leader was said to have had Islamist leanings.