A UN base has been petrol-bombed in Beni, east of the Democratic Republic of Congo, amid worsening protests against the UN.
At least two other peacekeeping bases were also targeted on Thursday.
Casualty figures were not immediately clear.
At least 19 people including three UN peacekeepers have died in the violent clashes following anti-UN protests that started on Monday.
Demonstrators have been accusing the UN of not protecting civilians against armed groups operating in the east.
A UN spokesman says the protesters have been joined by Mai Mai militia groups, formed ostensibly to protect villagers.
More than 100 different armed groups operate in the east, including the Allied Democratic Front that is affiliated to the Islamic State group.
A recent wave of attacks has killed hundreds and displaced tens of thousands.
The US has asked the government in the Democratic of Congo to protect UN peacekeepers and their facilities amid protests in the country.
Protests against the UN mission in the country, known as Monusco, have since Monday resulted in the deaths of 19 people – including three peacekeepers.
“We call on the national and local authorities in the [DR Congo] to ensure the protection of Monusco sites and personnel and for protesters to express their sentiments peacefully,” State Department spokesman Ned Price told reporters on Thursday.
The US said attacks against UN personnel and their sites was against international law and appreciated DR Congo government’s “commitment to investigating these events”.
Mr Price noted that Monusco serves “a critical role in fostering peace and security, protecting civilians, and facilitating delivery of humanitarian assistance”.