The International Olympic Committee (IOC) has expressed its confidence in the integrity of the Russian Anti-Doping Agency (RUSADA).

Just prior to the start of the Sochi 2014 Winter Olympics, the World Anti-Doping Agency (WADA) said that RUSADA had changed its approach, that its level of testing had "vastly increased" over the last four years since Vancouver 2010 and that it was doing its job in a "professional fashion".

And the IOC has echoed that assessment, while also thanking WADA for the work it has done with RUSADA.

Asked about RUSADA in a Sochi 2014 press conference on Saturday, IOC medical director Richard Budgett said: "There were concerns, and they were public, about the WADA-accredited laboratory in Moscow.

"Obviously the laboratory here in Sochi depends on that accreditation. It is a transfer of that accreditation - the laboratory director is the laboratory director here in Sochi. And I am glad to say that it is WADA-accredited.

"They had to produce really excellent protocols, they were under constant review and I have to pay tribute to and thank WADA for the amount of work they put into making sure the laboratory in Moscow had absolute integrity, and that we could guarantee that integrity.

"It was suggested to us that the IOC made doubly sure the laboratory in Sochi had governance that we were fully in control of.

"So we do have four of our own laboratory experts, laboratory directors from around the world, in there as well as a large number of experts from different laboratories.

"So there is a lot of assurance. You might be concerned the very large increase in samples that happens in a short period of time during an Olympic Games might put a strain on any policies or procedures that were there to ensure complete integrity.

"But we are absolutely confident that is protected and is safe."

Chairman of the IOC's medical commission Arne Ljungqvist said: "We are very grateful that WADA reviewed the situation since questions came up and could assure us the laboratory will work fully in compliance with the requirements during these Games."

Ljungqvist also said he was not surprised that no positive drugs tests had been announced since the start of the Games, adding: "It is expected, I would say, that people don't cheat and those that do are not here.

"In Vancouver four years ago we found just one, which shows that our programme is pretty efficient I would say and serves as a deterrent."

Meanwhile, the IOC said it had been assured by Sochi 2014 that the case of environmental activist Yevgeny Vitishko, who was jailed on Wednesday for three years, is not an Olympic-related matter.

It has been reported that Vitishko is critical of and seeking to highlight the environmental impact of the Sochi Games, and that an alleged breach of the terms of a suspended sentence given to him in 2012 for spray-painting a fence had led to it being converted into a prison term.

"As you know we have been following this case and we had raised it before," IOC spokesman Mark Adams said.

"We asked two days ago and we have had confirmation from Sochi, who got the information for us from the relevant authorities, that this is not Games-related.

"We understand Mr Vitishko was arrested after vandalising a house a few years ago. He was given a suspended sentence at the time for that and, subsequently, my understanding is that he broke that suspended sentence and was jailed.

"On this particular one, we have been assured that it is not Olympic-related."