"Overnight impacts in Donetsk and Avdiivka city centers. Unacceptable!" the OSCE SMM wrote on Facebook.
"The OSCE SMM is following up on reports about multiple civilian casualties. Sides have to stop fighting!" the report says.
Read alsoBritish reporter wounded in AvdiyivkaAs UNIAN reported earlier, Zhebrivsky, the head of the Donetsk regional military-civil administration of Ukraine, informed on Thursday about a new attack by the combined Russian-separatist forces on the Ukrainian town of Avdiyivka, where a stadium in the center of the town and a school, which was used as a humanitarian aid collection point, came under fire.
According to Zhebrivsky, one person was killed and another one was wounded in the shelling.
Read alsoKyiv debunks rumors about shelling of occupied DonetskHe later said in an update: "A wounded woman was found near the No. 2 school building, which came under fire. She was rushed to hospital but died of wounds. This is the second dead person in Avdiyivka in the past hour."