A Libyan national suspected by Egypt of involvement in last month's attack on the US consulate in Benghazi has been killed in a raid by Egyptian security forces in Cairo, a security official said.

Karim Ahmed Essam el-Azizi was killed on Wednesday in the raid in Cairo's eastern district of Nasr City that targeted him and other fighters with suspected links to al-Qaeda, the official said.

Four Egyptians were detained in the operation, he added.

Azizi was killed by a bomb he had tried to use against the security forces during the raid, the security official said.

It was not immediately clear what role Azizi had played in the assault on the US consulate on September 11, in which the ambassador, Chris Stevens, and three other Americans, were killed.

The security official said Azizi had been living in a rented apartment in Nasr City for the past three months.

He said police had found 15 bombs and various weapons, including assault rifles, in the Libyan's flat.

The attack on the Benghazi consulate has become a highly politicised issue in the US presidential election season.

It occurred during a wave of Muslim protests over an anti-Islam film produced in California, which also sparked violence against US diplomatic missions in Egypt and Tunisia.

However, official emails obtained by the Reuters news agency showed that the White House and the state department were advised two hours after the consulate attack that an Islamist group had claimed responsibility.

President Barack Obama and other US officials have acknowledged that the attack was a "terrorist" act by fighters with suspected links to al-Qaeda affiliates or sympathisers.