Three offshore lines of the Nord Stream gas pipeline system on the bed of the Baltic Sea sustained "unprecedented" damage in one day, Nord Stream AG, the operator of the network, said on Tuesday.

The bulletin was published after Sweden's Maritime Authority issued a warning about two leaks in the Nord Stream 1 pipeline, shortly after a leak in the nearby Nord Stream 2 pipeline was discovered on Monday that prompted Denmark to restrict shipping in a five nautical mile radius.

Kremlin spokesman Dmitry Peskov said Tuesday Russia was "extremely concerned" about the reported leaks in the gas pipelines of the Nord Stream system. "This is a completely unprecedented situation that requires urgent investigation. We are extremely concerned about this news," he said.

Asked by reporters whether it could be an act of sabotage, the spokesman said: "It is impossible to exclude any options. Obviously there is some kind of damage to the pipe, as for what caused it – before there are results of the investigations, no option can be ruled out."

The German economy ministry said it was investigating the cause for the pressure drop in Nord Stream 1, and added "we currently do not know the reason for the drop in pressure."

Nord Stream AG said it was impossible to estimate when the gas network system's working capability would be restored.

"The destruction that occurred on the same day simultaneously on three strings of the offshore gas pipelines of the Nord Stream system is unprecedented. It is not yet possible to estimate the timing of the restoration of the gas transport infrastructure," it said.

Nord Stream 1, which consists of two parallel lines with an installed capacity of 27.5 billion cubic meters per year each, started supplying gas directly from Russia to Germany in 2011.

Flows via the pipeline, which had been working at only 20 percent of its capacity since July, were halted at the end of August and were not relaunched following maintenance.

Nord Stream 2, which runs almost parallel to Nord Stream 1, was built in September 2021 but was never launched as Germany refused to certify it. The project was halted altogether just days before the start of Russia-Ukraine conflict on February 24.

(With input from agencies)