An explosion tore into a public bus in Cairo, wounding five people, according to Egyptian state television.

Officials say the blast happened on Thursday morning as the bus passed through Cairo's eastern Nasr City district. They said the cause was still uncertain but they suspected an explosive device was thrown at the bus or set nearby.

Egypt has seen a wave of attacks blamed on Islamic militants since July's ousting of Islamist president Mohammed Morsi and the subsequent crackdown on his Muslim Brotherhood group.

On Tuesday, a suicide car bomber struck a police headquarters in the Nile Delta city of Mansoura, killing 15 people – the worst bombing yet.