Russian President Vladimir Putin and his Ukrainian counterpart, Petro Poroshenko, are set to meet with the leaders of Germany and France in Minsk on Wednesday.

USA Today reported the four-way summit in the Belarusian capital is the result of a top-level diplomatic effort by German Chancellor Angela Merkel and French President François Hollande. They are trying to broker a peace deal to halt the fighting in eastern Ukraine, where pro-Russian separatists continue to battle government forces.

In a Cabinet meeting before his departure, Poroshenko said he would consider introducing martial law across Ukraine if "irresponsible actions" were to cause a further escalation of the conflict, CNN noted based on reports by the state-run Ukrinform news agency. The Minsk summit is "the most important one so far I have had as a president," he added.

Poroshenko said Ukrainians "demand an unconditional peace" and the withdrawal of all foreign troops from the country's territory but also expressed confidence that a compromise is within reach.

U.S. President Barack Obama, meanwhile, warned Putin that continued "aggressive actions" in Ukraine -- such as the military, financial and logistical support Washington says Moscow has been providing to the separatists -- would come with heavy costs, the Week said. Obama called his Russian counterpart on the eve of the latter's departure to Minsk, the White House revealed.

Clashes continued in eastern Ukraine even as the four leaders were headed to the capital of Belorussia, whose dictator Alexander Lukashenko is seen as a close ally of Putin's, USA Today noted.

In Donetsk, a city of almost a million inhabitants that functions as the self-declared capital of the separatist Donetsk People's Republic, three people were killed overnight, city officials said. On Tuesday, 16 people died and 48 were wounded in rocket strikes, reports of the Ukrainian government in Kiev indicated.

More than 5,400 individuals have already lost their lives in the conflict, while close to a million have been forced to leave their homes.

Increasingly desperate to end the violence, Merkel and Hollande embarked on a joint, high-stakes diplomatic effort last week as they flew to Kiev and Moscow. Nevertheless, a German government spokesman sought to dampen expectations for the Minsk summit

The meeting represented "a glimmer of hope," Steffen Seibert said, "but not more."

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