Allied Democratic Forces rebels with machetes and guns killed more than 50 civilians at a funeral in east Congo, the latest big attack by the Islamic State-linked group, officials said.

The ADF assault took place on Monday night in the town of Ntoyo in North Kivu province’s Lubero territory, said Macaire Sivikunula, a local administrator.

“I can confirm a provisional death toll of 50. The victims were caught off guard at a mourning ceremony in the village of Ntoyo at around 9 p.m., and most of them were killed with machetes,” he said. “The search is continuing.”

The ADF started as an uprising in Uganda but has been based in neighbouring Congo since the late 1990s, recognised by the Islamic State militant group as an affiliate.

A recent flurry of ADF attacks has added to insecurity in eastern Congo, a mineral-rich region where Rwanda-backed M23 rebels staged a major advance earlier this year, prompting U.S. President Donald Trump’s administration to try to broker peace.

Last month, the ADF killed more than 50 civilians in multiple attacks, while an ADF attack in July on a church left 38 dead.

Colonel Alain Kiwewa, the military administrator for Lubero, told Reuters that Monday night’s death toll was around 60 and could rise as there were still people missing.

As well as using machetes, the assailants also shot dead some victims and set fire to vehicles, said Samuel Kagheni, a local civil society leader.

Alain Kahindo Kinama, a resident, said Congolese soldiers had arrived at the scene on Tuesday morning and that many people were trying to leave the area.

Congolese army spokesperson Lieutenant Marc Elongo said ADF militants had “already committed the massacre” by the time soldiers intervened.

There was no immediate comment from the ADF.

On Monday, the group claimed credit for five recent attacks on Christian civilians and the Congolese and Ugandan armies, according to the SITE Intelligence Group.

Congo’s army and its ally Uganda say they have intensified operations against the ADF in recent weeks.