MOSCOW/BRUSSELS, Sept 29 (Reuters) - Russia said on Thursday 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.

The European Union is investigating the cause of the leaks in the Gazprom-led (GAZP.MM) Nord Stream 1 and 2 pipelines and has said it suspects sabotage was behind the damage off the coasts of Denmark and Sweden.

Four days after the leaks were first spotted, it remains unclear who might be behind any attack on the pipelines that Russia and European partners spent billions of dollars building.

Zakharova called for an EU investigation to be "objective", and said Washington would have to "explain itself" - a reference to President Joe Biden's comment in February that, if Russia invaded Ukraine, "there will no longer be a Nord Stream 2".

The White House has dismissed Russian allegations that it was responsible for the damage to Nord Stream and Biden's comments were referring to efforts at the time to secure certification to bring Nord Stream 2 into commercial use.

But the spokesperson for Nord Stream AG said it was not possible to give any forecasts for the pipeline's future operation until the damage had been assessed.

The European Union on Wednesday warned of a "robust and united response" should there be more attacks and stressed the need to protect its energy infrastructure, but EU officials have avoided pointing a figure directly at possible perpetrators.

The EU official said he expected the 27-nation bloc to agree parts of the sanctions package before the summit, such as the blacklisting of additional individuals and some of the trade restrictions with regard to steel and technology.