(CNN) A leader of pro-Russian rebels in eastern Ukraine's Donetsk region said Friday he is not interested in a truce with the Ukrainian government in Kiev because his troops are on the offensive.

"Since we're attacking, there is no sense to have peace talks now," Aleksandr Zakharchenko, leader of the self-proclaimed People's Republic of Donetsk, said in a meeting with university students, according to his media office.

"We've made this mistake before. It's not decent to repeat it," he said.

Thousands have been killed in months of conflict between the rebels and Ukrainian troops, and a ceasefire agreed to in September crumbled long ago. Zakharchenko's comments came two days after the foreign ministers of Ukraine and Russia met in Berlin to discuss a way out of the violence.

But Zakharchenko showed no interest in the talks.

"There will be no attempts from our side to talk about the ceasefire," he said, reported Russian state news agency RIA. "We will be on the offensive until we reach the border of Donetsk region."

He said that he was interested in cooperating with Ukraine on prisoner exchanges. "We need to get our guys who've been captured," he said, according to RIA.

Despite the talks in Berlin, violence in the breakaway Donetsk and Luhansk regions in eastern Ukraine shows no signs of abating.

Power is out in and around Luhansk after militants shelled a power plant there, Luhansk regional official Hennady Moskal told Ukraine's state-run Ukrinform news agency. Moskal noted that the local water supply and boilers are off, and trolley buses aren't operating.

Thursday's shelling of a transit stop in Donetsk city -- an attack that Ukraine's Defense Ministry blamed on rebels -- killed eight civilians, according to state news reports. But Ukrainian troops have come under heavy fire, as well.

That includes 115 attacks in a recent 24-hour period that killed three troops and wounded 50 more, Ukrinform reported Friday.

The news agency said that "Russian-terrorist troops" faced off with Ukrainian soldiers Thursday along Bakhumtka Highway, even posting a picture that showed a man with stripes on his clothing, suggesting that he was part of the Russian military.

This is in line with Kiev's repeated assertions that Russia has not only actively supported rebels with arms, but has sent its own troops across the border to battle Ukrainian forces. On Wednesday, for instance, Ukrainian President Petro Poroshenko said that "more than 9,000 Russian troops (crossed) our Russian-Ukrainian border, bring with them hundreds and hundreds of tanks, armed personnel carriers, and killing Ukrainian civilians and attacking Ukrainian troops."

Russian Foreign Minister Sergey Lavrov promptly responded to this assertion with a firm denial, much like other denials made by Russian officials in recent months over similar allegations of armed intervention.

"As to the flow of troops and armaments, this is not the first time we hear something like that," he said. "And each time I hear that, I say if you're so confident about that, please present us with facts, but no one has been able to provide us with these facts."

Pro-Russian separatists have claimed control of parts of eastern Ukraine since the spring of 2014, despite a push by Ukrainian forces to defeat them. From mid-April to January 21, the conflict had killed at least 5,086 people and injured at least 10,948 others, said the United Nations.

"We fear that the real figure may be considerably higher," the Office of the U.N. High Commissioner for Human Rights said about the death toll in a report released Friday.

At least 262 people were killed in the fighting from January 13 through Wednesday alone, the report said.

Unrest in Ukraine began with protests in the country's capital last year after President Viktor Yanukovych, favoring closer ties to Russia, dropped plans to sign a political and economic agreement with the European Union

After months of protests and days of deadly clashes between demonstrators and security personnel in Kiev, Parliament ousted Yanukovych in February. Weeks later, Russia annexed the Crimean Peninsula.

Then in April, violence broke out in two Ukrainian regions that border Russia -- Donetsk and Luhansk -- as separatist leaders declared independence from the government in Kiev.