An international monitoring team of six people came under shelling in the eastern Ukrainian city of Donetsk on Sunday amid an ongoing cease-fire between government forces and pro-Russian separatists, according to a new report. A cease-fire agreement was signed about 10 days ago between the warring factions in the region.

The shelling badly damaged two marked vehicles of the Organization for Security and Cooperation in Europe, or OSCE, but none of the team members were injured, Reuters reported, adding that the monitors had witnessed the body of a woman lying on the street in the market area.

“All six colleagues were able to get back to base but both vehicles were badly damaged,” Michael Bociurkiw, an OSCE spokesman, told Reuters. “We regard this as a very serious incident. It's the first time our vehicles have taken fire.”

According to a statement from OSCE, four shells exploded within 20 seconds of each other and about 650 feet from the monitoring team in a Donetsk market, which appeared to have been subjected to shelling prior to the team’s arrival. After the OSCE team moved to a different location about half a mile away from the market, another mortar shell reportedly exploded about 330 feet from the team’s new position.

Bociurkiw did not clarify who was behind the shelling attacks and it was also unclear if the OSCE monitors were deliberately targeted, according to Reuters. The region has seen sporadic violence between Ukrainian forces and separatist rebels despite the signing of a cease-fire agreement on Sept. 5.