Russian gas deliveries to the Balkans were severely disrupted yesterday after an explosion at a pipeline in Moldova, reinforcing worries about ageing energy infrastructure in the region.

The explosion in Transdniestr, a breakaway region of Moldova, cut supplies to the Balkans by 40 per cent, Russian state-run gas giant Gazprom said.

Officials in Transdniestr said the blast was likely an accident rather than an act of sabotage.

The explosion left a crater 10 metres wide and caused a wide area to be sealed off by firefighters. Flames from the ensuing fire could be seen several kilometres away.

An AFP correspondent at the scene said that all trees and vegetation in the area had been blackened and burned within a radius of around 500 metres.

"At around five in the morning I was woken up by a huge explosion. I saw massive flames," said Zhenya, a local from Kitskanu, the village nearest the blast. A large military lorry was seen carting away huge pieces of the ruptured pipeline.

"The volume of the gas reduction is around 40 per cent. Gas deliveries are being carried out through parallel gas pipelines," Gazprom said in a statement. The blast affected one of the three pipelines used to supply natural gas to the Balkans, cutting daily supplies to the region from 40 million cubic metres to 24 million cubic metres, said a spokesman for Ukraine's Naftogaz.

"We are trying to boost transit through the other two branches but we cannot pump more than the capacity of the pipes," the spokesman, Valentin Zemlyansky, said. Naftogaz said that full gas supplies had been restored to Bulgaria, Greece, Macedonia and Turkey by the afternoon via other pipelines but Gazprom insisted they were still reduced by 40 per cent.