On Thursday, Ukrainian government forces and pro-Russian separatists accused each other of violating the ceasefire in the Lugansk region (east of the country).
The head of the so-called breakaway republic of Lugansk, Leonid Baschnik, accused government forces of targeting residential areas in Luhansk with mortars.
The President of the (pro-Russian) Lugansk Republic - in the Donbass region in eastern Ukraine - called on international observers to document these developments and take urgent measures to prevent bloodshed in the Donbass, as he put it.
The Russian Interfax news agency quoted representatives of the Lugansk region in the Ukrainian-Russian ceasefire monitoring group as saying that "the Ukrainian armed forces have crudely violated the ceasefire regime, using heavy weapons that the Minsk agreements stipulate that they must be withdrawn."
On the other hand, the Ukrainian government forces denied today, Thursday, accusations of targeting separatist sites in the east of the country.
"Despite the fact that our positions came under fire with prohibited weapons, including 122mm artillery, the Ukrainian forces did not fire in response," the officer in charge of communicating with the media told Reuters by phone.
Recent years have seen sporadic shootings from both sides in separatist-held areas, but any escalation of the years-long conflict with the Donbass separatists could stoke tension between Russia and the West.
Yesterday, Tuesday, the Russian State Duma (parliament) approved a resolution to submit a proposal to President Vladimir Putin to recognize the independence of the "Republics of Donetsk and Lugansk" in eastern Ukraine.
Russian-backed separatists unilaterally declared the independence of Donetsk and Luhansk provinces from Ukraine in the spring of 2014.
The Donetsk and Lugansk regions are located in the conflict-torn eastern Donbass basin, which has been partially controlled by Russian-backed separatists since 2013.
The warring parties in eastern Ukraine in February 2015 - in the Belarusian capital, Minsk - reached a ceasefire agreement, providing for the withdrawal of heavy weapons and foreign forces, in addition to Ukraine's control of its entire border with Russia by the end of 2015, which has not yet been achieved.
Relations between Kiev and Moscow were strained against the backdrop of Russia's illegal annexation of Ukraine's Crimea and its support for separatists loyal to it in the Donbass.
Recently, Western countries have accused Russia of amassing its forces near the Ukrainian border, and Washington has threatened to impose sanctions on Russia if it "launches" an attack on Ukraine.