Russian President Vladimir Putin said the "unprecedented sabotage" against the Nord Stream gas pipelines was "an act of international terrorism," the Kremlin said in a statement.
Putin had made the remarks in phone call with his Turkish counterpart Tayyip Erdogan.
Separately Russia has said that leaks spewing gas into the Baltic Sea from pipelines to Germany appeared to be the result of state-sponsored "terrorism", as an EU official said the incident had fundamentally changed the nature of the conflict in Ukraine.
