The clashes come a day after President Petro Poroshenko said negotiations had started in Kiev among representatives of Ukraine, Russia, and the Organization for Security and Cooperation in Europe.

Loud booms and shelling were heard in downtown Slovyansk, where at least six buildings bore damage from shelling a day earlier. The city has been an epicenter of a nearly two-month standoff between Ukrainian forces and pro-Russia rebels, who have seized administrative buildings, police stations, and border posts across the region.

SLOVYANSK, Ukraine — Government forces on Monday traded fire with pro-Russia separatists who control an eastern Ukraine city after the country’s new president announced daily negotiations were underway toward ending the conflict.


Poroshenko said that the meeting focused on strengthening the porous Ukraine-Russia border, adding that the fighting must cease by the end of the week. While he promised the negotiators would meet daily until the crisis was resolved, he did not say whether results had been achieved on Sunday.

The European security organization, whose rotating presidency is held by Switzerland, said Heidi Tagliavini, a Swiss diplomat who has worked on crises in Chechnya and Georgia, was its representative in the negotiations. Poroshenko’s office said Russia’s ambassador to Ukraine and the Ukrainian ambassador to Germany also took part.

On Monday, Ukraine’s acting defense minister, Mykhailo Koval, told journalists that Poroshenko was working toward bringing the conflict to an end ‘‘in the quickest time period,’’ according to the Interfax news agency. He did not give a specific date.

Russia has repeatedly called for Ukraine to end its operation in the east, while Ukraine has blamed Russia for fomenting tensions in the region and backing the rebels materially.

Fighting resumed Monday in Slovyansk, where residents said at least six buildings — including a gas station, two shopping centers, and two apartment buildings — had been hit by mortars a day earlier.


Andriy, a local plainclothes policeman who wouldn’t give his last name, was standing with other officers in uniform near the debris.

‘‘Yesterday the center of the city was hit the hardest,’’ he said. ‘‘There were a lot of injured people, and a lot of buildings were hit that haven’t been hit before.’’

Dozens of cars carrying civilians were seen leaving the city by road, and a bus with a sign in the windshield reading ‘‘children’’ left the city on Monday. The UN Refugee Agency estimated in late May that at least 10,000 people in Ukraine were internal refugees, a figure that has undoubtedly grown as both Ukrainian and pro-Russia sides dig in.

Russian Prime Minister Dmitry Medvedev said Monday his government was providing aid to Ukrainian refugees within Russia.

He had previously estimated there were about 4,000 such refugees.

‘‘They will end the shooting only when they erase us from the face of the planet, when nothing remains here but a flat space,’’ said Svetlana, a 52-year-old resident of Slovyansk who would not give her last name. ‘‘Only then the war will be finished.’’

Rebels have held the Ukrainian government responsible for the rising number of civilian casualties in the conflict, while the Kiev leadership says the insurgents have attacked civilians in order to foment resentment against the government.

Government officials say at least 200 people — most of whom were civilians — have been killed in the conflict so far.


The spokesman for Ukraine’s operation in the east, Vladislav Seleznev, wrote on Facebook late Sunday that the separatists were responsible for the shelling in Slovyansk.

In a separate development Monday, Russian and Ukrainian officials met in Brussels to seek a solution to a dispute over energy that has led to concerns about cutoffs of natural gas to the European Union.

The talks, organized by the European Commission, are intended to broker an agreement on how much Ukraine should pay Russia for gas already consumed and for future consumption.

The meeting between Russia’s energy minister, Alexander Novak, and his Ukrainian counterpart, Yuriy Prodan, was the fifth of its kind since talks began in early May after Gazprom, the Russian state-controlled energy company, raised the price of gas to Ukraine by 80 percent in March and threatened to cut off supplies if it did not pay up.

The price rose after Russia annexed Crimea and imposed an export tariff that had been waived as a form of payment for the lease of the Black Sea fleet there.

In response to the reimposition of the export tariff, Ukraine ceased payments on its natural gas bills, prompting Gazprom to threaten to cut off domestic shipments.