World

Ukraine mourns 13 victims of bus blast that government blames on Russian-backed separatists

  • In this Wednesday, Jan. 14, 2015 photo Russian-backed separatist's tank is placed in a fortified position at the check-point north of Luhansk, Eastern Ukraine.  An attack on a passenger bus in eastern Ukraine killed 12 people Tuesday, likely dealing the final blow to hopes that a short-lived and shaky cease-fire could take hold. (AP Photo/ Mstyslav Chernov)

    In this Wednesday, Jan. 14, 2015 photo Russian-backed separatist's tank is placed in a fortified position at the check-point north of Luhansk, Eastern Ukraine. An attack on a passenger bus in eastern Ukraine killed 12 people Tuesday, likely dealing the final blow to hopes that a short-lived and shaky cease-fire could take hold. (AP Photo/ Mstyslav Chernov)  (The Associated Press)

  • In this Wednesday, Jan. 14, 2015 photo Russian-backed separatist sit on top a tank at the check-point north of Luhansk, Eastern Ukraine.  An attack on a passenger bus in eastern Ukraine killed 12 people Tuesday, likely dealing the final blow to hopes that a short-lived and shaky cease-fire could take hold. (AP Photo/ Mstyslav Chernov)

    In this Wednesday, Jan. 14, 2015 photo Russian-backed separatist sit on top a tank at the check-point north of Luhansk, Eastern Ukraine. An attack on a passenger bus in eastern Ukraine killed 12 people Tuesday, likely dealing the final blow to hopes that a short-lived and shaky cease-fire could take hold. (AP Photo/ Mstyslav Chernov)  (The Associated Press)

  • In this Wednesday, Jan. 14, 2015 photo Russian-backed separatist walks past tanks at the check-point north of Luhansk, Eastern Ukraine.  An attack on a passenger bus in eastern Ukraine killed 12 people Tuesday, likely dealing the final blow to hopes that a short-lived and shaky cease-fire could take hold. (AP Photo/ Mstyslav Chernov)

    In this Wednesday, Jan. 14, 2015 photo Russian-backed separatist walks past tanks at the check-point north of Luhansk, Eastern Ukraine. An attack on a passenger bus in eastern Ukraine killed 12 people Tuesday, likely dealing the final blow to hopes that a short-lived and shaky cease-fire could take hold. (AP Photo/ Mstyslav Chernov)  (The Associated Press)

Ukraine is holding a day of mourning after 13 people were killed when a bus was hit by what the government says was a shell fired by Russian-backed separatists.

President Petro Poroshenko said respects would be paid Thursday for all people killed by rebel military offensives in eastern Ukraine.

Separatists deny responsibility for the deaths and accuse Ukrainian forces of staging an attack near the town of Volnovakha to smear them. Russia media has speculated the blast was provoked by an anti-personnel mine.

Surveillance camera footage filmed during Tuesday's incident shows shells falling near the bus, although the vehicle is not seen in shot. Monitors from the Organization for Security and Cooperation in Europe said the bus showed "damage consistent with a nearby rocket impact."