Security officials say a roadside bomb went off on a busy downtown Cairo street, killing two policemen and a passer-by near the foreign ministry.

They said the Sunday explosion targeted a police checkpoint near the back entrance of the Nile-side ministry building, and that another two people were wounded in the blast.

They spoke on condition of anonymity because they were not authorized to speak to the media.

Egypt has faced a campaign of violence by radical Islamists since last year's ouster of President Mohammed Morsi. The campaign has mostly targeted security forces, first in the Sinai Peninsula, but more recently in the capital, the Nile delta and remote parts of the country, like the western desert.