At least 10 people were killed overnight in a raid on the city of Beni in eastern Congo, witnesses said, and a civil society group and a monitoring body said Islamist militants were suspected of being behind the attack.
Residents said a group of attackers had set several houses on fire in the middle of the night in the city's Beu district, firing upon people as they exited the buildings and attacking some with machetes.
The raid took place just four days after the city, home to thousands of displaced people who fled surrounding areas because of violence, was hit by two blasts, which officials also blamed on the Islamists.
Hundreds of people took to Beni's streets on Thursday morning to protest against the government's failure to protect the city. Some people built makeshift barricades while others burned tyres.
"So far we have seen ten bodies ourselves and have just transported a body on a cart to the morgue," said protestor Kathembo Ngeleza, who was woken up by gunfire during the night after attending a party celebrating Congo's Independence Day.
"We don't know what our authorities are doing. The idea is to protect the inhabitants, but here we are again ... We are really angry," he added.
Gloire Kivetya, president of a body representing civil society groups in Beni's Beu district, blamed the attack on the Allied Democratic Forces (ADF), an Islamist militant group that claims links to Islamic State. The Kivu Security Tracker, also said the ADF was suspected.
There was no immediate claim of responsibility, and the ADF could not be reached. The ADF has been accused of killing thousands of people since 2014, mostly in more remote areas.
The army blamed the ADF for two explosions that hit Beni on Sunday, in which only an attacker was killed. The city's mayor closed schools, churches and markets for 48 hours as a safety precaution.
The government declared martial law in North Kivu and Ituri, two provinces bordering Uganda, at the beginning of May, in an attempt to quell a surge in violence.
But the number of civilians killed in such attacks has increased since then, according to the Kivu Security Tracker, which maps unrest in eastern Congo.
There are nearly 700,000 internally displaced people in Beni territory, 57,000 of whom are in the city itself, the United Nations said in a report on Tuesday.