German Chancellor Angela Merkel on Tuesday said all coronavirus vaccines "are welcome" in the EU once they have received regulatory approval, after Russia's Sputnik V jab was found to be 91.6 percent effective in trial results.

"Every vaccine is welcome in the European Union," Merkel said in an interview with German broadcaster ARD, as the bloc faces growing anger over a sluggish start to its inoculation campaign.

The veteran leader stressed however that all jabs must first be authorised by the European Medicines Agency (EMA), whose decisions can only be reached with "the necessary data".

"Today we have read good data for the Russian vaccine too," Merkel said. 

She repeated that she had recently spoken to Russian President Vladimir Putin about the Sputnik vaccine, a conversation that fuelled hope another jab could be added to speed up efforts to end the pandemic.

Merkel said on January 21 that Germany had offered to assist Russia with its application process at the EMA, through Germany's Paul Ehrlich Institute.

"And if this vaccine is approved by the EMA, then we can talk about joint production or also about usage," Merkel said at the time.

Sputnik V -- named after the Soviet-era satellite -- was approved in Russia months before results from its final-stage clinical trials were published, leading to scepticism from experts.

But the new analysis of data from 20,000 Phase 3 trail participants, published in The Lancet medical journal, suggests that the two-dose vaccination offers more than 90 percent efficacy against symptomatic Covid-19.  

The encouraging results come at a time when the bloc's vaccine drive is dogged by supply bottlenecks and delivery delays.

In the ARD interview, Merkel again said that although the United States, Israel and Britain were further along with their vaccinations, Germany had been right to opt for a more cautious EU-wide approach.

While supply of the BioNTech/Pfizer and Moderna jabs will remain tight in the first quarter of 2021, Merkel insisted the pace would pick up later in the year, once production issues are resolved and more vaccine candidates are approved.

The outgoing chancellor renewed her promise that Germany was on track to offer every German a Covid-19 jab by late September.

But she also urged Germans "to hold their nerve a little while longer" and keep complying with tough curbs on public life, set to stay in place until at least mid-February.

"We still have a long way to go, and the hardest stretch is this winter," Merkel said.