Sweden's coastguard said on Thursday it had discovered a fourth gas leak on the damaged Nord Stream pipelines earlier this week, after ruptures first reported on Monday sent gas spewing into the Baltic Sea. The European Union suspects sabotage was behind the leaks on the subsea Russian pipelines to Europe, and has promised a "robust" response to any intentional disruption of its energy infrastructure. The leak reported on Thursday is the second one found in Swedish waters, while two others were discovered in Danish waters.