The man who detonated the bomb that killed three tourists in Cairo last week was a student who adopted extreme religious views after the death of his father, the Interior Ministry said on Monday. Hassan Rafaat Ahmed Bashandi, born in 1987, carried out the bombing in which he was killed in an old Cairo market on Thursday evening, the ministry said in a statement.

"There is no information or indication that point to his having connections with others, but the investigation continues," the statement said.

Egypt's authorities have been anxious to limit the fallout of the blast for fear of it harming the tourism industry, the No. 1 source of foreign exchange. From the outset, government officials have said the attack was likely to be the work of either one person or a small group of individuals.

The attack heightened an already tense political atmosphere in Egypt. Opposition groups condemned the attack but warned the government against using it as a pretext to clamp down on political reform.

The banned group Al-Gamaa al-Islamiyya, or Islamic Group, one of the two major militant groups that carried out most of the violent attacks that hit Egypt in the 1990s, issued a weekend statement condemning the attack.

Egypt's largest Islamic opposition group, the Muslim Brotherhood, also condemned "the cowardly act." The group, banned since 1954, has said it renounced violence in the 1970s.

Kifaya, or Enough, a recently created movement that has demonstrated since December against a possible additional term for Egyptian President Hosni Mubarak, also denounced the bombing.

But the group warned "against using these kinds of criminal incidents in desperate attempts to prolong despotism and oppression, or using them as a pretext to justify the continuation of emergency laws."

The blast near the Khan al-Khalili market killed two French citizens and an American man and wounded 18 other people.

"All indications show that the device exploded prematurely while the culprit was preparing the explosives," the Interior Ministry said, adding that Bashandi was carrying about 3 kilograms of TNT in a leather bag with a lot of nails.

The ministry said that after Bashandi's father died in August, he began to exhibit extreme religious positions, such as forbidding his family from watching television.

In his home, police found CDs containing data downloaded from the Internet on waging Islamic holy war and building bombs from materials that are freely available. At his aunt's house, where Bashandi occasionally stayed, police found 43 fireworks from which the gunpowder had been removed.

Prosecutors said earlier Monday that police had arrested Bashandi's mother and two brothers. Police have detained up to 30 people in connection with the blast, police officers have said, speaking on customary condition of anonymity.

Upstairs neighbors of Bashandi in Shoubra, a low-to-middle income district in Cairo, said Monday they could not believe he was responsible for the bombing.

A detective involved in the investigation said on Monday that the breakthrough in identifying the bomber came after his uncle contacted the authorities after seeing a photograph of the corpse in a weekend newspaper.

The pro-opposition newspaper Al-Wafd published a photo of the suspected bomber's mutilated body on its front page on Saturday.

The uncle told police that he thought the corpse belonged to his nephew who had disappeared 24 hours before Thursday's bombing, the detective said, speaking on condition of anonymity.

DNA samples from the uncle and the nephew's mother matched that of the corpse, the detective said.