Shortfalls in gas imports from Russia could force Italian energy giant ENI to start cutting off supplies to corporate customers from Thursday, ENI said, as a minister described the situation as "critical".

"We are in an emergency and we have reacted to this emergency by increasing gas imports from Algeria and from northern Europe via Switzerland," ENI chief executive Paolo Scaroni told radio news channel Radio 24 on Monday.

"We won't have problems until Wednesday," Scaroni said.

The ENI boss said: "We are expecting another cold wave in Russia and we don't know how (Russian gas giant) Gazprom will behave on Thursday and Friday. We are preparing for difficult times ahead."

He said the first companies to be cut off would be those "that have contracts that allow for an interruption in gas flows."

The shortfall in gas imports from Russia was 11 percent on Wednesday, 24 percent on Thursday, 29 percent on Friday, 29 percent on Saturday and 22 percent on Sunday, figures from the Snam Rete gas network showed.

"The situation is certainly critical because the flows from Russia and France have diminished but the situation is being monitored," Economic Development Minister Corrado Passera told reporters.

"Yesterday we passed into a state of emergency because consumption was at its highest ever and so we have to be ready for demand being even higher than forecast," he said.

Gazprom on Saturday said it could not pump additional gas to Western Europe following drops in supplies registered in Austria, Bulgaria, Germany, Greece, Hungary, Italy, Poland, Romania and Slovakia.