NATO released a joint statement on Thursday that said any attack on members' critical infrastructure would result in a "united and determined response".
The 30-member alliance, which has included Estonia since 2004, said the damage to the Nord Stream 1 and 2 gas pipelines is of "deep concern".
"All currently available information indicates that this is the result of deliberate, reckless, and irresponsible acts of sabotage," the statement said.
NATO said the leaks are causing risks to shipping and substantial environmental damage. It supports investigations underway to determine the origin of the damage.
Members are committed to "prepare for, deter and defend against the coercive use of energy and other hybrid tactics by state and non-state actors".
"Any deliberate attack against Allies' critical infrastructure would be met with a united and determined response," the statement said.
Earlier this week, Denmark and Sweden reported gas leaks in the Nord Stream 1 and 2 pipelines.
The German ambassador to the UK, Miguel Berger, told the BBC it was clear that a non-state actor could not have been behind the incidents - in other words, a country must have been responsible.
The EU has repeatedly accused Russia of using gas supplies as a weapon against the West, in retaliation for its support for Ukraine.
Russia dismissed suggestions that it had attacked its own pipelines as "predictable and stupid".
Editor: Helen Wright