Fighting raged in eastern Ukraine Wednesday, killing five people at a bus station in the rebel stronghold of Donetsk, as Western leaders confirmed that they would take part in peace talks later in the day.
Steffen Seibert, a spokesman for German Chancellor Angela Merkel, said she and French President Francois Hollande would travel to the Belarusian capital, Minsk, to attend the four-way summit with Russian President Vladimir Putin and Ukrainian President Petro Poroshenko.
European leaders have warned that there is no guarantee a deal will be reached with Moscow, which the West says is fueling a separatist rising in eastern Ukraine with troops and arms. Germany and France have rushed to mediate after a recent uptick in violence in the region, where fighting has killed at least 5,300 people since April.
In Donetsk, rebel officials said that five people were killed and nine wounded in a shelling attack early Wednesday on a bus station, where an Associated Press reporter saw one body. Donetsk city officials said in a statement that three people had been killed in shelling overnight.
Officials in Kiev said Wednesday that 19 troops had been killed and 78 wounded in a day of fighting in Debaltseve, a hotly contested transport hub in the region.
Poroshenko posted a statement on his website saying that he had made an impromptu visit to the region early Wednesday. He stopped in the city of Kramatorsk, some 30 miles (50 kilometers) from the nearest front line, where Kiev says 16 people were killed and 48 wounded in a rocket strike Tuesday.
"We demand an unconditional peace," Poroshenko said. "We demand a cease-fire, a withdrawal of all foreign troops, and closing of the border.... We will find a compromise within the country."
Later, in comments carried by Interfax-Ukraine news agency, Poroshenko said he was "ready to impose martial law across the country if we are not able to reach an agreement today in Minsk."
At a news conference in Moscow, Russian Foreign Minister Sergey Lavrov said that there was "notable progress" in the peace process, but gave no details.
Lavrov said the most important goal of the talks would be to implement a cease-fire, and that it would be impossible for Ukraine to re-establish its control over the border with Russia.
"In these conditions, to give away the Russian part of the border also would be to cut them (the rebels) off even from humanitarian help and allow them to be surrounded," Lavrov said.
French Foreign Minister Laurent Fabius said early Wednesday that "quite a number of problems remain" in negotiations, including the future of eastern Ukraine, guarantees about the Ukraine-Russia border, and the prospects of a possible cease-fire, weapons pullback and prisoner exchange.
Fabius said the aim of the talks is to win an accord, but "not just one on paper."
Yuras Karmanau in Minsk, Belarus, and Laura Mills in Moscow contributed to this report.