A convoy carrying refugees away from the military conflict in the eastern Ukrainian city of Luhansk has reportedly come under attack.
It's unclear at this point on the number of casualties, or which faction might be responsible.
Ukrainian government forces are accusing the rebels in Luhansk of firing a rocket into the convoy.
The accusation is being rejected by the rebels.
This comes as government forces press their military offensive in rebel-held eastern cities.
Kiev claims government forces have advanced into Luhansk for the first time in months.
Ukrainian authorities have reportedly raised the national flag over a police station in the city.
Meanwhile, in the city of Donetsk, rebels there say they are standing firm as the government troops move on.
In another development, Russia says an agreement has reached to allow a humanitarian convoy into eastern Ukraine.
The announcement has been made following a series of meetings this weekend among Russia, Germany, Ukraine and France in Berlin.
Russian Foreign Minister Sergei Lavrov:
"There is certain progress. First of all we formed a consensus regarding the delivery of humanitarian aid to the population of eastern Ukraine. We can declare that all the issues, many of which were artificially imposed, regarding us sending about 300 trucks with humanitarian aid, were resolved. The agreement has been reached with the Ukrainian side as well as with International Committee of the Red Cross and we expect this aid to be delivered to those who need it."
The 4-way talks are expected to continue this week.
However, no progress has been made toward a ceasefire or any political end to the fighting in eastern Ukraine.
Russia and Ukraine have been at loggerheads for days over a convoy of 280 Russian trucks carrying humanitarian aid to eastern Ukraine.
Kiev says it's worried the convoy could be a Trojan Horse for Russia to get weapons to the rebels.
Russia has dismissed the claim.
The convoy has been parked near the Ukraine border for days.
