Image caption Jesse Ryder had been due to join the Indian Premier League

New Zealand cricketer Jesse Ryder is in a medically induced coma after being attacked twice in quick succession as he left a Christchurch bar, police say.

He is believed to have suffered serious head injuries after the assaults and is now in intensive care.

Local media quoted doctors as saying that Ryder suffered a fractured skull and a collapsed lung.

He was in Christchurch playing for Wellington against Canterbury in the domestic one-day competition.

The 28-year-old cricketer had been due to fly to Delhi to start his $300,000 (£200,000) contract in the Indian Premier League.

Ryder has a history of disciplinary lapses and alcohol-related incidents. Although he had been drinking before the assault on Thursday morning, police said alcohol was not a factor.

The cricketer had chosen not to play for New Zealand since the Napier ODI against South Africa in February 2012 after he was disciplined by team management for breaking team protocol by being out drinking while carrying an injury.

Jesse Ryder- troubled cricketer Middle-order left-handed batsman for Tests and an opening ODI batsman

Has made 1,269 runs in 18 Tests at an average of 40.93 with a highest score of 201 and 1,100 runs in 39 ODIs

Has recently been in scintillating form for the Wellington Firebirds

Was disciplined in February 2012 by New Zealand team management for drinking while carrying an injury

Had to withdraw from the test series against England in 2008 after cutting his hand on a window at a Christchurch nightclub

"It appears that Jesse has been the victim of a serious assault and suffered head injuries as a result," Detective Senior Sergeant Brian Archer told a nationally televised news conference.

"Jesse was taken to hospital where he remains in intensive care in a critical condition in an induced coma after suffering multiple injuries."

Mr Archer said that "two or three men" carried out the attacks on the cricketer - but he did not think that alcohol was a "contributing factor".

A witness to the assaults told New Zealand's One News that she could hear the impact of the blows from inside the bar.

"As soon as the fight started there were probably four or five guys that ran out to pull them off him and hold them back while he stumbled off over the road," the witness said.

Mr Archer said that Ryder was attacked again by one of the men after he moved across the road.

He said that no weapon was believed to have been used and that so far no motive had been established for the attack.

"At this stage we have not identified the people involved in the incident but are following positive lines of inquiry," he added.

"We are asking for witnesses to come forward and to speak to us about it."

Ryder's friends and domestic and international cricketers have been sending messages of support via social media.

The attack has been condemned by Prime Minister John Key, who expressed his shock over the "sinister" incident.