Ukrainian authorities claimed successes and large casualty numbers against separatist rebels in the east, including re-establishing government control in the port city of Mariupol.
More than 40 fighters were killed near Stepanivka, a village close to the Russian border, the Defence Ministry said in Kiev. The Ministry added that its troops destroyed numerous armoured vehicles and two tanks that belonged to the separatists.
There was no immediate response from the separatists.
Interior Minister Arsen Avakov said a day earlier that the pro-Russian militants had brought at least three tanks from Russia.
Experts were, however, quick to point out that the separatists had probably taken the tanks from a Ukrainian depot, as photos and video footage showed vintage Soviet T-64 tanks that are no longer in service in Russia but still used by the Ukrainian armed forces.
Mr. Avakov said on Friday on Facebook that government forces had taken Mariupol back under control and hoisted the Ukrainian flag over the city administration building.
A separatist representative told the Russian Interfax news agency that five of their fighters were killed in the pre-dawn operation.
Mr. Avakov said two soldiers were wounded and that 11 separatists had been arrested.
Control over Mariupol, an industrial city on the Sea of Azov, had been going back and forth between the separatists and commanders loyal to the government over the past two six weeks.
President Petro Poroshenko praised the “heroism of the Ukrainian military” in Mariupol and ordered the Donetsk regional administration to move its temporary headquarters there.
Governor Serhiy Taruta earlier moved his office from Donetsk to Kiev out of safety concerns.
Mr. Taruta’s government building has served as the headquarters to the separatist “Donetsk People’s Republic” since its proclamation in early April.
The leader of the Donetsk separatists, Denis Pushilin, said that a car bombing late on Thursday was an assassination attempt against him.
“Our opponents are well known. This was most likely done by the Ukrainians,” he told Interfax.
Three people were killed and four wounded when the bomb went off.
Among the victims was an aide and a bodyguard to Mr. Pushilin. It was the second attempt on Mr. Pushilin’s life in the past two weeks.
Meanwhile, E.U. Energy Commissioner Guenther Oettinger said he expects gas talks between Russia and Ukraine to resume on Saturday.
“My hope is that we can continue tomorrow,” he told journalists on the margins of an EU energy ministers’ meeting in Luxembourg, adding that he expects Ukraine and Russia to be represented by their energy ministers and the chiefs of their respective gas companies.
The talks could be held in “Brussels or Berlin or Kiev or Moscow”, he added.
The Russian Energy Ministry said later that no talks were planned for the weekend. “We are waiting for payment to be delivered by Monday morning,” an unidentified Ministry spokesman was quoted as saying by Interfax.
Russia has said that it will deliver gas only for pre-payment after a deadline that has been postponed several times - and is now set for Monday.
Also on Friday, the European Commission released 250 million euros (338 million dollars) to Ukraine as part of a programme to support institutions and reforms in the country. The European Union has pledged a total of 11 billion euros to help Ukraine in coming years.
