Image copyright AFP Image caption The blast occurred just before 11:00 local time during the children's playtime

Twelve children have been injured, two of them seriously, in a grenade attack on a school in Benghazi, officials say.

Witnesses say the grenade was thrown over a wall into a private school in the Tabilinu area during a break from lessons.

Benghazi has witnessed a series of bomb attacks and assassinations within the past year, but attacks on schools are rare.

It is not yet known who is responsible for the attack.

A Benghazi resident told the BBC that a family member had seen a man rip out the grenade pin with his mouth.

He then threw it into the school before escaping in a low black car with tinted windows, the eyewitness said.

People were running and screaming after the blast, the resident said.

The attack was carried out just before 11:00 local time (09:00 GMT), while the children were outside playing.

A Benghazi security official said the explosion was "weak" and that police were currently looking for the perpetrators.

Benghazi was the cradle of the 2011 uprising that toppled the 42-year rule of Muammar Gaddafi.

But since then it has been a focal point for attacks on public institutions and officials.