Russian Foreign Minister Sergei Lavrov said on Tuesday it would be "unusual" to hold a presidential election in Ukraine while the army was being deployed against Ukrainians.
"Scheduling elections in times when the army is used against parts of the population is not conventional," he told a news conference on Tuesday at a Council of Europe meeting in Vienna. "This is not Afghanistan."
"We will see how this process ends," he said.
Lavrov said Ukraine should agree a new constitution to define presidential powers before people went to cast their ballots.
Ukraine\’s Interior Minister says 30 pro-Russian insurgents were killed during Monday\’s military assault to expunge anti-government forces in the eastern town of Slovyansk.
Arsen Avakov said Tuesday that four government troops also died and another 20 were injured during the gun battles.
Separately on Tuesday, authorities suspended flights in and out of eastern Ukraine\’s industrial hub of Donetsk. It is unclear why the flights were suspended or how long the suspensions were to remain in effect.
With violence on the rise in Ukraine, United Nations Secretary-General Ban Ki-moon has told the French News Agency he will offer himself as a mediator before the situation creates huge consequences beyond anybody\’s control.
Ukraine is facing its worst crisis in decades as citizens fight over whether to look toward Europe or improve ties with Russia. Pro-Russian separatists control about a dozen eastern Ukrainian towns and cities, demanding the right to vote on whether to split with Ukraine and join Russia.
A similar referendum in Crimea in March led to the Russian annexation of the Ukrainian peninsula and the current crisis.
Russia\’s Foreign Ministry is calling on Ukraine to withdraw its troops from the east and open talks on ways to resolve the political crisis.
Interim Ukrainian Prime Minister Arseniy Yatsenyuk accuses Russia of seeking to destroy Ukraine by engineering what he says is a "well-planned provocation" against the government.
Russia says the new Ukrainian government is controlled by anti-Russian nationalists and neo-Nazis. It says it has the right to protect Russian speakers.
On Tuesday, British Foreign Minister William Hague, who was also in Vienna for the Council of Europe meeting, accused Russia of trying to prevent or disrupt Ukraine\’s May 25 presidential election.
And French President Francois Hollande warned Tuesday that there will be "chaos and the risk of civil war" if the May 25 vote is not held.
Forty-six people died in the Black Sea city on Friday in a fire at an official building and fighting between pro-Russian and pro-Ukrainian protesters.
The 25 May presidential election was called after pro-Kremlin President Viktor Yanukovych was overthrown by pro-Western protesters in February.