CAIRO, Feb 3 (Aswat Masriya) - An Improvised Explosive Device went off in the vicinity of Talaat Harb Square in downtown Cairo early Tuesday, leaving no reported casualties behind, a security source said.

Alaa Abdel Zaher, head of the explosives administration at the Cairo Security Headquarters, told Aswat Masriya the explosion occurred at a passage near the square.

Deputy Interior Minister Khaled Youssef meanwhile told state-run news agency MENA that the blast was caused by a sound bomb at the Baehler passage.

The explosion was loudly heard in the neighbourhood of downtown Cairo, eye-witnesses said. It came shortly after two explosive devices were discovered at the Cairo International Airport.

Airport security sources told Aswat Masriya two explosive devices were found at the airport terminals, prompting the authorities to increase security alert. Both devices were dismantled before they exploded.

Violence erupted nationwide starting last week, ahead of the fourth anniversary of the January 2011 uprising which toppled the regime of former President Hosni Mubarak. The anniversary day, Sunday, was marred by violence, with at least 23 reported deaths nationwide.

Several explosions have been reported nationwide since then.