The worst February cold spell Europe has seen in decades may last until the end of the month, leading meteorologists said, raising the prospect of further deaths and an extended spike in European spot gas prices.

We do have higher confidence in a change by mid-February, but not to milder weather, Leon Brown, a meteorologist at The Weather Channel in Britain, told Reuters. February will probably remain a cold month right to the end.

The cold and heavy snowfall has killed hundreds of people across Europe. The temperature in some eastern countries has plummeted to nearly minus 40 degrees Celsius.

More than 130 villages remained without electricity in Bulgaria on Wednesday and the army was delivering food and medicines, the Defence Ministry said.

Bulgaria declared Wednesday a day of mourning for eight people who died after melting snow caused a dam to burst, flooding an entire village. Two people are missing.

The European Union's crisis response chief Kristalina Georgieva said the worst of the flooding was yet to come.

In Bosnia, authorities reported five more deaths from the cold and snow on Wednesday, taking the total to 13.

In Serbia, where 13 people have died and 70,000 are cut off by snow, authorities urged people to remove icicles from roofs after a woman in Belgrade was killed by falling ice.

An energy official in Serbia said while demand for electricity had soared, ice was hampering production in some hydro-power plants and coal trains were struggling to run.

A Croatian radio station said high winds had deposited fish from the Adriatic sea onto the island of Pag. Instead of going fishing or to the market, people are taking their shopping bags and collecting fish on the shore, Zadar radio reported.

NO EARLY THAW

Cold polar air from northern Russia flanking an area of high pressure has prevented warmer weather from moving in across the Atlantic over Europe, plunging a wide swathe of the continent into sub-zero temperatures for much of the past 10 days.

Officials from the World Meteorological Organization (WMO), speaking in Geneva this week, did not rule out the possibility of cold temperatures lasting for the rest of February.

Omar Baddour, who coordinates the WMO's climate data monitoring programme, said there was a chance the pressure system might start lifting next week, but said it could remain until the end of the month.

A difference in pressure between Europe and the Arctic known as a negative Arctic oscillation, part of the cause of the freezing weather, is expected to take two or three weeks to return to equilibrium, Baddour said, meaning there may be no early thaw.

While the phenomenon of the high-pressure system itself is not unusual, the dramatic turn to below-normal temperatures after weeks of mild weather took experts by surprise.

It's actually quite unique and a bit baffling how this winter has developed, Brown said. It's unusual for it to develop so suddenly and have it become a persistent block toward the end of January and February.

The cold spell is the strongest one to happen in the month of February in 26 years, said Georg Mueller, a forecaster at Point Carbon, a Thomson Reuters company.

It was in 1986 when we had the last similarly severe cold weather (in February), Mueller said.

The sheer size of the current Siberian blocking pattern has made it difficult to predict how it will move, Brown said.

In this instance this big blocking of cold air ... seemed to influence the way the winds behaved rather than the other way around, he said. We didn't expect the cold block to become so persistent and then move westward.

Computer models are having trouble making forecasts for when the system will clear out of Europe, Brown said.

The cold snap has driven British gas prices up to their highest levels since 2006, hitting above 100 pence per therm on Tuesday, a surge of more than 15 percent.

Russia curtailed gas exports to Europe last week as demand reached all-time highs, forcing countries like Italy to increase imports from Algeria and extract stored gas.

Protracted cold temperatures and increased domestic demand could force Russia to cut its exports to Europe again.

(Additional reporting by Tom Miles; Editing by Janet Lawrence)