Suspected Boko Haram suicide bombers have killed at least 13 other people in an attack on a market in the northeast Nigerian town of Biu in Borno state, officials said on Saturday.

The blasts struck while aid workers were distributing food to people affected by the eight-year conflict with Boko Haram, said Aliyu Idrisa, a community leader.

In addition to the 13 victims, 53 people were injured and two bombers were killed, said Victor Isuku, police spokesman for Borno state.

Saturday’s attack bore the hallmarks of Boko Haram, which uses suicide bombers, often women and girls, to attack crowded public spaces.

Last week, a suicide bombing at a mosque in the northeastern town of Mubi killed at least 50 people, one of the deadliest attacks in recent years.

The government has said its long-term plan for the northeast is to corral civilians inside fortified garrison towns and effectively cede the countryside to Boko Haram.

That plan and a string of deadly attacks have raised questions about assertions by the Nigerian government and military that Boko Haram’s Islamist insurgency has been all but wiped out.