An explosion has struck a pipeline near the eastern Ukrainian city of Poltava.
Witnesses say the flame is reaching 200 meter high, RIA Novosti reports.
The Urengoy–Pomary–Uzhgorod natural gas pipeline is about one kilometer way from the nearest settlement.
No victims have been reported. Fire fighters crews have been deployed.
Relations between Russia and Ukraine have entered a new stage and are "moving closer towards a serious conflict", said State Duma Foreign Affairs Committee chief Aleksei Pushkov.
Russia did not recognise unilateral border demarcation by Ukraine which was "contrary to all norms of international law", Russia's ITAR-TASS news agency quoted Pushkov as saying Tuesday.
"An attack on the Russian embassy, an attempted attack on the consulate-general in Odessa, insults to the Russian president, regular arrests of Russian journalists -- I think this is a deliberate decision co-ordinated with the U.S -- all these are links of one chain," he said.