Kyiv said the Kremlin built up military forces near their shared border and violated a ceasefire. But Russia warned that a new military conflict would "destroy" Ukraine.
Ukraine demanded on Thursday that Russia halts escalating military tensions and reaffirms its commitment to a ceasefire in the eastern Donbass region.
Kyiv had earlier accused Moscow of building up military forces near their shared border, and said that pro-Russian separatists were violating a ceasefire.
"Russia's current escalation is systemic, largest in recent years," Ukrainian Foreign Minister Dmytro Kuleba said in a statement.
"Russia's actions have brought the situation to a dead end. The only way out is diplomacy," Kuleba added, assuring that Ukraine preferred talks to violence.
The Organization for Security and Cooperation in Europe (OSCE) recorded hundreds of ceasefire violations in the past few days, including 493 on March 26 alone.
Russia argued that it was entitled to move its troops within its territory.
"It should not worry anyone and does not pose a threat to anyone," Kremlin spokesman Dmitry Peskov said on Thursday.
Meanwhile, Russia's foreign minister, Sergey Lavrov, warned that any attempts to start a new military conflict over the Donbass region could "destroy" Ukraine, the Russian TASS news agency reported.
"The military understands the harmfulness of any action to unleash a hot conflict. I very much hope that they will not be prompted by politicians, who, in turn, will incite the West, led by the United States," Lavrov was quoted as saying.
Since 2014, Russia's annexation of Crimea not only triggered a deadly conflict with Ukraine, but also strained the Kremlin's ties with Western nations.
The European Union on Thursday accused Russia of launching a conscription campaign in Crimea, deeming it a "violation of international humanitarian law."
NATO also slammed Russia's military build-up near the Ukrainian borders, according to Reuters news agency.
"Russia's destabilizing actions undermine efforts to de-escalate tensions," a NATO official told Reuters.
On Wednesday, the United States expressed concern over the situation in eastern Ukraine. Pentagon press secretary John Kirby said the US was aware of escalations by Russian troops on Ukrainian borders in recent days.
According to Kyiv, the conflict between Ukrainian troops and Russian-backed forces in Donbass has killed at least 14,000 people since 2014.
fb/msh (AFP, AP, Reuters)