KIEV, (AFP) -- Two pro-Russian rebels were killed and another injured in fresh clashes with government forces in the country's war-torn east as simmering violence showed little sign of abating, separatist authorities said on Thursday.

The new casualties came the day after Ukraine scored a major diplomatic  victory by securing the return of Ukrainian pilot Nadiya Savchenko as part of a  prisoner swap with the Kremlin.

Senior rebel commander Eduard Basurin said Ukrainian forces attacked rebel positions near the town of Avdiivka located some 10 kilometres (6 miles) north of the rebels' de facto capital Donetsk.

"During the attack two soldiers of the Donetsk People's Republic were killed and one injured", he told reporters.

Kiev military spokesman Oleksandr Motuzyanyk said the situation around Donetsk had been tense over the past day.

"As a result of hostilities, Ukraine's armed forces did not sustain any casualties but two of our soldiers were wounded", Motuzyanyk told reporters.

Citing data received as of May 24, the OSCE Special Monitoring Mission to Ukraine said in a report Thursday that its monitors had recorded "an increased number of ceasefire violations" in the Donetsk region "compared to the previous reporting period".

Persistent violence is preventing the warring sides from reaching a firm political reconciliation deal despite a series of truce agreements that have helped reduce the fighting over the past few months.

Some commentators expressed the hope that the high-profile Savchenko prisoner swap would help reduce tensions between the two rivals and speed up the implementation of Western-brokered agreements to reach peace in the east of the ex-Soviet country.

Savchenko, who had been held in captivity in Russia for nearly two years, was convicted by a Russian court in March over the killing of two Russian journalists in eastern Ukraine and sentenced to 22 years behind bars.

Around 9,300 people have died and more than 21,000 injured since the mainly Russian-speaking regions revolted against Ukraine's new pro-Western government in April 2014.

Kiev and the West have accused Russia of buttressing the rebels and sending in regular troops across the border, claims Moscow has repeatedly denied.