Ukraine military, Russia-backed separatists accuse each other of attacks
Any escalation in Kiev's years-long conflict with the rebels could fuel fresh tensions between Russia and the West and worsen the ongoing standoff.
Russian-backed separatists in eastern Ukraine have accused government forces of opening fire on their territory and said they are trying to establish if anyone was hurt or killed.
Ukraine's military has denied the accusations that government troops attacked four times in the past 24 hours, saying it was the rebels who shelled the Ukrainian military.
It was not immediately clear how serious Thursday's incidents were.
There was no immediate reaction from the Organization for Security and Cooperation in Europe (OSCE), which has been monitoring the situation in eastern Ukraine but has pulled out some of its monitors in recent days.
Artillery shelling was heard on Thursday near Donetsk airport and Elenovka, a village in Donetsk province — both parts of eastern Ukraine controlled by Russian-backed rebels, a witness told Reuters.
Such incidents of violation of ceasefire agreements between the rebels — who seized a swath of territory in eastern Ukraine in 2014 — and Kiev have occurred many times over the past eight years.
But this clash comes at a time when Russia has massed more than 100,000 troops close to Ukraine's borders while demanding that NATO pledge not to accept Ukraine as a member.
US intelligence agencies said this month they believed Russia might fabricate a pretext for an invasion of Ukraine, possibly by producing videos showing a staged attack. Russia dismissed that.
READ MORE: US warns of ‘some global fallout’ from Russia sanctions over Ukraine
Violation of ceasefire agreement
The assertions about shelling were made in a statement issued by representatives of the self-proclaimed Luhansk People's Republic.
It said Ukrainian forces had used mortars, grenade launchers and a machine gun in four separate incidents on Thursday.
"Armed forces of Ukraine have crudely violated the ceasefire regime, using heavy weapons, which, according to the Minsk agreements, should be withdrawn," the separatists said in the statement.
Russia's lower house of parliament voted on Tuesday to ask President Vladimir Putin to recognise the two self-proclaimed separatist republics in eastern Ukraine as independent.
The Kremlin has signalled Putin has no immediate plans to do that.
Western countries have accused Moscow of planning an invasion of Ukraine. Russia, which has been threatened with sanctions by the West, denies plotting any attacks.
Russia said this week it was pulling back some troops from areas adjacent to Ukraine after concluding exercises, but Western countries said they had seen no evidence of any meaningful withdrawal.
READ MORE: West seeks concrete Russian withdrawal as Ukraine celebrates 'Unity Day'