Egyptian security officials say that an explosion has gone off near a military facility in the countryside northeast of Cairo.

Witnesses say ambulances carried four soldiers to hospital, and one wall of the building was damaged. They spoke on condition of anonymity for security reasons.

Initial reports suggest that the Sunday explosion was caused by a hand grenade thrown at the building in Anshas, a village in Sharqiya province that houses a number of military facilities. The officials spoke anonymously in line with regulations.

Attacks on security targets have become frequent following the July 3 ouster of Islamist President Mohammed Morsi. A Sinai-based militant group has claimed responsibility for a Tuesday car bomb at a Nile Delta security headquarters that killed 16.