The World Anti-Doping Agency has registered 400 cases after a flood of information from new whistleblowers, and added on Friday it supports a U.S. assessment that a 2016 hack of the agency was perpetrated by the Russian state.

The head of WADA's investigations unit, Guenter Younger, said the agency has been approached by numerous whistleblowers in the wake of Russian doping scandals, which were sparked by insiders revealing widespread doping and cover-ups.

Younger said he was "overwhelmed" with information after WADA opened a whistleblower hotline in March 2017.

"More and more whistleblowers come and they say, `Now we are happy that we have someone that we can talk to,"' said Younger, a German policeman who investigated Russian doping cases for WADA and later took charge of its investigation unit permanently. "I thought perhaps a few, but we have so many. We have 400 cases registered."

Younger said the whistleblowers include "many" Russians, adding, "It was the Russians that took their system down and we as well need to acknowledge that and help them as well, that they can come back as clean athletes."

Younger said that, despite the hack of WADA in 2016, its systems were now secure.

Separately, WADA spokeswoman James Fitzgerald said the agency backed the assessment in a U.S. indictment unsealed on Thursday of hackers working for the Russian state military intelligence agency targeted WADA and accessed athletes' medical records.

"We have no reason to disagree with that assessment and, in fact, we've held that view all along," Fitzgerald said on Twitter.

Decision could be reversed

WADA reinstated the Russian anti-doping agency last month, making it easier for Russian athletes to compete abroad and for the country to host competitions. That decision could yet be reversed if Russia reneges on a promise to provide data from a Moscow anti-doping lab which could contain key evidence of earlier over-ups.

Speaking on Friday alongside Younger at a conference organized by the International Olympic Committee, IOC athletes' committee head Kirsty Coventry said Olympians had been rude to Russians who competed in neutral uniforms at this year's Winter Olympics.

Coventry said the Russians deserved more respect, citing an IOC vetting process which allowed 168 Russians to compete as "Olympic Athletes from Russia" when the national team was suspended over doping scandals.

"I was disgusted at how some of the athletes were treating the OAR team in Pyeongchang," said Coventry, a former swimmer who serves in Zimbabwe's government. "It was awful to see and those athletes had gone through vigorous steps in being able to go and compete and were probably more clean than any of the other athletes there from some of the big nations."

Of the four doping cases at the Pyeongchang Olympics, two involved Russian curlers Alexander Krushelnitsky and Nadezhda Sergeeva, who were disqualified. The other cases involved a Slovenian ice hockey player and a Japanese speedskater.