One civilian was also killed. At least three of the injured transported to a nearby hospital were in grave condition, a local officials said.
The attack took place near the town of Katwiguru, around 100 km (60 miles) north of the provincial capital, Goma.
"We had information of attempted attacks by FDLR [Democratic Forces for the Liberation of Rwanda] along the same axis the day before," Van Den Wildenberg said, adding that one police officer was killed and another was injured during efforts to secure the road on Friday.
"So far we have confirmed a total of three confirmed killed, and it may be more," she said, adding UN peacekeepers were stepping up patrols in the area.
Fighting has recently flared in North Kivu, long a flash point both during and after Congo's 1998-2003 war, following a deal ironically designed to finally bring peace to the volatile province which shares a border with Rwanda.
After Joseph Kabila won Congo's first democratic presidential elections in more than four decades, the army and Rwandan mediators began talks to bring dissident Laurent Nkunda, a dissident Tutsi, and his troops into existing army brigades stationed in North Kivu in January.
But instead of ending the violence, the five new mixed brigades began hunting down Nkunda's enemies, the FDLR.