MOSCOW: Moscow on Sunday suffered its worst fire in decades when a gas pipeline blast sent flames bursting into the sky and raised new concerns about the security of Russia's ageing energy infrastructure.

The fire produced spectacular plumes of yellow flames reaching 200 metres (600 feet) high and huge clouds billowing smoke were visible against the night sky, television pictures showed.

Moscow mayor Yuri Luzhkov, who rushed to the scene, said that five people had been injured in the fire, including one man who received 35-percent burns, but there had been no fatalities.

The cause of the fire was almost certainly to be technical in nature, he added, virtually ruling out the possibility of foul play.

"In my opinion, 99 percent sure, this was a technical catastrophe. This all still needs to be investigated," he said in comments on state television.

"The cause could have been an upsurge of pressure in the pipeline, as a result of which an explosion took place underground," he added.

"I don't remember there ever being a fire like this in Moscow," added deputy mayor Petr Birukov, while the Interfax news agency quoted other officials as saying it was the worst in two decades.

The fire broke out at 0030 local time (2030 GMT Saturday) and at its peak sent flames 200 metres high into the sky. But by the morning the blaze had been brought under control and the flames reduced to 20 metres, officials said.

The emergencies ministry said the fire was a category five on its scale for assessing such incidents, the most serious level possible. It said that 35 fire brigade units had been sent to the scene.

"All of our efforts are directed towards reducing the temperature around the centre of the fire," said deputy emergency situations minister Alexander Chupriyan, predicting that it would be put out by midday.

The city's energy system would not be affected, Birukov added. But the municipal telecoms firm said that 80,000 customers had lost their phone connection after nearby underground cables were damaged by high temperatures.

The authorities halted all traffic in the immediate area around the fire close to the Michurinsky Avenue in southwest Moscow, a key artery that leads towards the Moscow River in the centre if the city, RIA Novosti quoted traffic police as saying.

There was no threat to nearby apartment blocks, with the nearest building an administrative building 200 metres (yards) away and a 19-storey apartment block half a kilometre distant.

Two dozen cars parked in the vicinity were damaged but no-one was inside them at the time.

Dozens of local residents, who had been up late celebrating Saturday's holiday to mark the defeat of Nazi Germany in World War II, emerged to watch the fire from a safe distance with many recording the event on camcorders.

Officials were also at pains to emphasize that preparations for the finals of the Eurovision Song Contest, due to take place in the capital next weekend not far from the scene of the blast, would not be affected.

Such fires are frequent events throughout the former Soviet Union due to ageing pipeline infrastructure that has not been renewed in decades.

Pipeline blasts in ex-Soviet Moldova and Turkmenistan in April both caused by technical mishaps severely disrupted gas supplies.