Sweden's security agency says leaks from two undersea gas pipelines linking Russia and Germany were caused by detonations.

The Swedish Security Service said on Thursday investigators were analyzing material to determine who was behind the leaks from the Nord Stream pipelines.

The pipelines suffered four leaks in the Baltic Sea late last month. The Swedish agency has been looking into two leaks which took place in the country's exclusive economic zone. The Danish government is examining the other two.

There are growing suspicions among European countries that the pipelines were sabotaged. Russian President Vladimir Putin has blamed Western nations.