Kiev, Sep 27 (IANS/EFE): Ukrainian authorities have uncovered three mass grave sites in the eastern city of Slaviansk, which had been under the control of independence-seeking pro-Russian militia, officials said.

"We located three mass graves. Bodies have been exhumed and sent to coroners for autopsy and identifying the cause of death," Andrei Lysenko, a spokesman for the National Security and Defence Council, told reporters Friday.

The spokesman added that a preliminary examination of the bodies suggests that those found in the sites might have died in the early summer months, when the city was under the separatists' control.

Pro-Russian separatist forces reported earlier this week that several mass grave sites containing the remains of civilians have been found with indications they were shot execution-style in the back of the head.

The Russian foreign ministry lost no time in denouncing the alleged massacres and called on the international community to open a rigorous investigation to clarify the circumstances under which the victims met their deaths.