An email to rent the boat in the pipeline attacks came from Ukraine, according to investigators

Metadata from emails used to rent a yacht suspected of being involved in the explosions that damaged the Nord Stream pipelines transporting natural gas last year implicates Ukrainian nationals, Germany's Der Spiegel newspaper reported on Friday.

In March, Der Spiegel claimed a yacht called 'Andromeda' had allegedly been used by a team of divers to sabotage the Nord Stream pipelines. The publication cited the discovery of traces of explosives in the cabin of the vessel and fake identification documents that were used in the hiring of the boat. 

The outlet's most recent report indicates that metadata from an email sent to enquire about the renting of the yacht "leads to Ukraine." The president of a presumed shell company through which the yacht was rented also lives in Kiev, according to German broadcasters NDR and WDR, as well as other media sources in the EU country. 

Der Spiegel also wrote on Friday that investigators were probing if the attack could have been undertaken by an independent group of Ukrainian commandos or if the sabotage would likely have been authorized by Kiev. The Ukrainian government, meanwhile, has denied all links to the explosions. 

To date, no group - state body or otherwise - has accepted responsibility for September's explosions, which came soon after Moscow reduced gas supplies to Europe following the implementation of a wave of Western sanctions on Russia over its military operation in Ukraine. 

In February, the Pulitzer Prize-winning investigative journalist Seymour Hersh detailed in an extensive report evidence he claimed linked Washington to the attacks, which he said were conducted in tandem with figures in Norway. 

Moscow - which was accused of orchestrating the blasts as a 'false flag' event by some in the West - on Thursday summoned the ambassadors of Germany, Sweden, and Denmark in protest over what the Russian Foreign Ministry called a "complete lack of results" in an investigation into the source of the blasts. 

"It has been noted that these countries are not interested in establishing the true circumstances of this sabotage," Moscow's foreign ministry spokesperson said on Thursday, adding that investigators were delaying their efforts and attempting to "conceal the tracks" of the true perpetrators.