Russia started supplying gas to rebel-held eastern Ukraine on Thursday after Kiev had temporarily suspended deliveries because of damage to the networks from heavy fighting, which is continuing despite a cease-fire.

The spat over Russian gas supplies and pricing for Ukraine had been at the heart of the broader standoff between the two former Soviet states, which spilled over into a chill in Moscow's relations with the West.

Responding to an order from Russian Prime Minister Dmitry Medvedev to supply gas to east Ukraine as humanitarian aid, gas company Gazprom said it had started supplies via the Prokhorovka and Platovo pumping stations on the border with east Ukraine.

Gazprom Chief Executive Officer Alexei Miller said gas deliveries were reaching 12 million cu. meters of gas per day.

Sergei Kupriyanov, a Gazprom spokesman, said the 12 million was in addition to the 30 million cu. meters per day Ukraine was already receiving, taking total deliveries to 42 million cu. meters per day.

He declined to comment further, saying the additional supplies were being shipped under an existing contract with Ukrainian state company Naftogaz.

Naftogaz said it had suspended supplies on Feb. 18 "due to the extensive damage of the gas transport networks."

Later on Thursday Naftogaz CEO Andriy Kobolev said the firm had resumed gas supply, but with smaller volumes. The firm has also said Russian gas exports via Ukraine have not been hampered.

Relations between Russian and Ukraine have soured since Moscow annexed the Crimea Peninsula and Kiev accused the Kremlin of supporting rebels fighting government troops in east Ukraine. Russia denies arming the rebels.

Russian supplies of gas to Ukraine have further complicated relations after Moscow cut supplies last year over unpaid bills. Supplies resumed in December but Gazprom says Ukraine still owes $2.44 billion — a figure Kiev disputes.