EU sets ceasefire deadline as Ukraine joins bloc

Meanwhile, according to a report from Kiev, four international observers from the Organisation for Security and Cooperation in Europe (OSCE), taken captive in Ukraine a month ago, have been released, the Vienna-based organisation confirmed Friday.

According to the OSCE, the group of monitors, kidnapped in the Donetsk region in eastern Ukraine, was released unharmed late Thursday. However, the OSCE said another group that went missing in the neighbouring Lugansk region May 29 is yet to be freed, Xinhua reported.

The OSCE said its monitors were overseeing the situation in Ukraine's restive regions, though the number of observers was reduced due to the unstable security situation.

Meanwhile, five Ukrainian soldiers were killed in overnight attacks on checkpoints in the Donetsk region despite a ceasefire which expires Friday.

"The attacks and shootings on Ukrainian armed forces positions are continuing. Throughout the past 24 hours, the terrorists committed assaults against 11 Ukrainian checkpoints," Andriy Lysenko, spokesman of the National Defence and Security Council, told reporters.

According to him, the Ukrainian military had repulsed all the attacks on its positions, which are regarded as gateways to the four towns of Slavyansk, Kramatorsk, Artemovsk and Kryva Luka.

At least 150 government soldiers and scores of insurgents had been killed since the violent confrontation erupted in eastern Ukraine in April.

President Petro Poroshenko announced a unilateral ceasefire by the government forces last Friday, and two days later the insurgents agreed to observe the truce.

However, the insurgents had allegedly continued their attacks on the Ukrainian troops during the week-long ceasefire, killing at least 20.