The gas export monopoly is struggling to meet export commitments as a severe cold spell drives up gas demand for heating in Russia and across Europe. Moscow is expected to face temperatures averaging minus 20 degrees Celsius for the next 10 days. 

"Some nominations were higher than we can put in the pipe," the source said. "The increase is due to higher nominations which we have already for more than a week."   

Gazprom supplies around a quarter of Europe's gas imports, and cuts to Europe in the past, mainly over pricing rows with transit countries such as Ukraine, have raised concerns over the security of supply from Russia. 

Earlier on Wednesday the company said in a statement that it was adhering to long-term contracts with European clients after reports of restricted supply.  

"Despite increasing gas consumption in Russia due to heavy frosts, Gazprom continues implementing its contractual obligations to European clients," it said in e-mailed comments. 

According to reports on Tuesday, Gazprom restricted supplies to Europe, its largest foreign market, to cover an increase in domestic demand.
 
GAS FLOWS HIKE? 

The European Commission on Tuesday said that gas supplies into Italy via the Austrian border had been reduced by 10 percent compared with normal levels.

The commission has said it had enough natural gas to make up for any shortfall and was confident demand could be met.  

For its part, Gazprom said that the Blue Stream underwater pipeline to Turkey is pumping at full capacity, while gas flows via Yamal-Europe pipeline, which has an annual capacity of 33 billion cubic metres, have been increased by 20 percent from last week.  

"In order to fulfill export obligations, the company has involved all the gas exporting routes and significantly increased offtake from its underground storage facilities in Europe," it said. 

Russia supplied Europe with 150 bcm of gas last year and expects to increase that to around 164 bcm in 2012.