MAIDUGURI, Nigeria (Reuters) - Two girl suicide bombers killed at least three people and wounded 17 at a market in the northeastern Nigerian city of Maiduguri on Sunday, a spokesman for state emergency agency NEMA, Sani Datti, said.

Residents said about nine people had been killed.

Boko Haram Islamists have been waging an insurgency for seven years in the region to try to establish an Islamic state.

The jihadists have frequently targeted crowded areas - such as markets, places of worship and refugee camps - in suicide bomb attacks across northeast Nigeria and in neighbouring Cameroon and Niger.

They have killed some 15,000 people and forced more than two million people to flee their homes.

Nigeria’s army has pushed the militant group back to its stronghold in the vast Sambisa forest in the past few months but the group still stages suicide bombings.