Last updated on .From the section Winter Olympics

Bach was speaking just five days before the Winter Olympics begin

XXIII Olympic Winter Games Venue: Pyeongchang, South Korea Dates: 9-25 February Coverage: Watch live on BBC TV, Red Button, Connected TVs, BBC Sport website and mobile app.

A decision to lift life bans for doping on 28 Russian athletes was "extremely disappointing and surprising", says International Olympic Committee chief Thomas Bach.

On Thursday, the Court of Arbitration for Sport (Cas) overturned the suspensions of 28 Russians, and partially upheld 11 other appeals.

"We would never have expected this," said the 64-year-old German.

He said Olympic officials had asked Cas for an explanation for their ruling.

Cas ruled there was "insufficient" evidence the athletes had benefited from a system of state-sponsored doping at the 2014 Winter Games, hosted by Russia.

Speaking at a news conference in Pyeongchang, South Korea, five days before the opening of the Winter Olympics, Bach said the IOC had been told no full explanation of the verdict would be released until the end of February.

He said the IOC knew only what had been released by Cas in a statement and that this was "extremely unsatisfactory given the gravity of the cases".

"We feel this decision shows the urgent need for reforms in the internal structure of Cas," he added.

Bach said the IOC would consider appealing against the ruling once it had seen the full reasoning behind Cas's decision.

The IOC has also turned down a request for 13 of the 28 athletes cleared by Cas - and two coaches - to be invited to take part in Pyeongchang.

A special IOC panel was set up to look at the request but it "agreed that the decision of the Cas had not lifted the suspicion of doping or given the panel sufficient confidence to recommend that those 13 athletes could be considered as clean".

Earlier, Bach had said: "The absence of sanctions by Cas does not mean that you are entitled to receive an invitation from the IOC because receiving this invitation is a privilege of clean Russian athletes."

British IOC member Adam Pengilly has called the Cas decision "a desperate and dark day for sport, with cheats and thieves allowed to triumph".