Tensions between Russia and Ukraine escalated after Ukrainian forces successfully repelled an attack by pro-Russian rebels on Donetsk Airport last week.
The Guardian newspaper reported that on Friday, a large plume of black smoke was seen from the airport after it came under heavy artillery fire. The city was witness to continuous rocket fire near the airport, with some shells hitting the surrounding residential buildings. However, no casualties were reported.
The heavy fighting around Donetsk, which is a stronghold of the rebels, led the Ukrainian prime minister Arseniy Yatsenyuk to call on world leaders asking them not to trust Russian president Vladimir Putin, despite his decision to sign a truce to end the five month-long war.
Yatsenyuk said that Russia wanted to create a state of perpetual war.
As cited in the Guardian, he said: "We are still in a stage of war and the key aggressor is the Russian Federation. Putin wants another frozen conflict in eastern Ukraine.
"His aim is not just to take Donetsk and Lugansk. His goal is to take the entire Ukraine. Russia is a threat to the global order and to the security of Europe."
A truce was signed between the two countries on 5 September. However, the BBC quoted Russian officials as saying that a Russian aid convoy had entered Ukraine. There is a fear among Western officials that such convoys may contain military equipment to help the rebels.
However, Russia maintains that the vehicles contained humanitarian supplies.