As the floodlights go off on important landmarks and gas-powered taxis are forced off the road, Bulgaria is demanding the right to crank up one of its Soviet-era nuclear reactors.

The poorest state in the European Union is also the worst hit by the gas-pricing row between Moscow and Kiev that has seen Russian gas supplies cut off to at least a dozen countries in Central and Eastern Europe.

In the coldest week of the year, more than 15,000 households have already lost all heating. Two million more, whose heat is produced in gas-fired central heating plants, have suffered from a dramatic drop in pressure that has left them shivering.

The Government appealed to Bulgarians today to cut back on gas usage. Supplies to almost all industrial customers have already been suspended. In Sofia, the heaters have been turned off on all public transport and gas-powered taxis — which make up about half of the total — have been ordered off the streets.

Although electrical supplies can still be met, users have been asked to exercise caution as consumers switch to electricity for their heating needs. Sofia turned off the lighting on the facades of public buildings such as parliament and the national theatre in order to save electricity.

"This is an absurd situation for the 21st century,” Petar Dimitrov, the Economy and Energy Minister, told the national broadcaster bTV. “Russia and Ukraine must find a quick solution . . . as the economies of half of Europe are at risk.”

Bulgaria receives 92 per cent of its gas from Russia via Ukraine and, unlike Turkey and Greece, has no access to any other gas routes. Out of a total population of 7.6 million, about 2 million people have heating that comes from gas-fired central heating plants, which have lowered steam pressure significantly.

“The only solution for Bulgaria is the resuming of deliveries. There is only one gas pipe entering the country and that is via Ukraine,” Mr Dimitrov said.

The country is making up for the cut in Russian supplies by pumping gas from its only underground storage at Chiren, in the northwest, which currently holds 570 million cubic metres of gas. Estimates vary, but experts calculate that the reserves could last for anything between one and three months.

A longer-term solution was mooted yesterday by the Bulgarian President, Georgi Purvanov, who suggested that a mothballed reactor at the Kozloduy nuclear plant be fired up again.

Bulgaria shut down four of six reactors at Kozluduy as a condition of its accession to the European Union, which considered the reactors too dangerous, but Mr Purvanov said that the No 3 generator, shut down in late 2006, should be started up because "a more critical situation is hardly possible".

An EU spokesman said that it saw no reason to reverse its stance on the reactors but the proposal has gone down well in Bulgaria itself, where newspapers threw their weight behind the campaign.

Temperatures across Bulgaria dropped to minus 16C (3F) and forecasters in the Balkan state say that the cold spell will continue for at least a week.

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