Pakistan cricketer Mohammad Amir has been released from jail after serving half of a six-month sentence for his part in a fixing scam.

Amir, 19, who had been tipped to become one of the all-time great fast bowlers, was freed from Portland Prison in Dorset this morning, sources said.

He was one of three Pakistan cricketers who received prison terms at London's Southwark Crown Court in November over a scandal that rocked world sport.

Ex-Test captain Salman Butt, 27, was jailed for two-and-a-half years for his role as the "orchestrator" of a plot to bowl deliberate no-balls in the 2010 Lord's Test against England.

Former world number two Test bowler Mohammad Asif, 28, received a 12-month prison term for delivering one of the fraudulent no-balls.

Mazhar Majeed, 36, the corrupt London-based sports agent at the heart of the fixing scandal, was jailed for two years and eight months.

All three players are also serving five-year bans from cricket imposed by the International Cricket Council (ICC).

The fixing scandal emerged after an undercover News of the World reporter approached Majeed in August 2010 pretending to be a wealthy Indian businessman seeking major international cricketers for a tournament.

The agent, from Croydon, south London, was secretly filmed accepting £150,000 in cash from the journalist as part of an arrangement to rig games.

Majeed promised the reporter that Asif and Amir would deliver three no-balls at specific points during the Test between Pakistan and England at Lord's from August 26 to 29 2010.

He claimed he had been carrying out fixing for two-and-a-half years and had seven players from Pakistan's national side working for him.

The trial judge, Mr Justice Cooke, said Amir was "unsophisticated, uneducated and impressionable" and "readily leant on by others", but noted there was evidence that he also discussed rigging an earlier match with a betting contact in Pakistan.

He alluded to the young bowler's claim that he and his family had faced threats over his part in the fixing, and said this was supported by ICC evidence about the strength of the "underworld influences" who control illegal betting overseas.

Amir, who admitted bowling two intentional no-balls at Lord's, was named player of the series for his spells of wicket-taking against England in the summer of 2010.

He became the youngest cricketer ever to take 50 Test wickets and thrilled the crowds during the tour with his ability to rip through top-order batsmen.

Many commentators have expressed regret at the waste of his exceptional promise and voiced hope that he will one day have a second chance to display his talents on the cricket pitch.

Amir and Butt failed in an attempt to have their sentences reduced at the Court of Appeal in November.