SINGAPORE - A cabby threatened to post revealing photos of a couple on YouTube after finding them on a phone left in the back of his taxi.

Mohamed Rafee Abdul Rahman, 33, tried to get $10,000 out of Zayed Moyeen in return for not revealing images of his brother Omar and his fiancee in their underwear.

On Friday the former driver was sentenced to four months' jail after admitting criminal intimidation, though he is planning to appeal.

District Judge Lim Keng Yeow said the crime was committed in a "grossly reprehensible" manner.

The court heard that after Rafee had a picked up Mr Omar from Changi Airport in the early hours of January 12, a couple who later took the cab found his phone and handed it to the cabby.

He charged it up and found the intimate pictures. Using apps on the phone he sent the photos to Mr Omar's fiancee and mother.

Rafee also threatened his 27-year-old brother Mr Zayed, an Indian national who was in Bangladesh at the time, saying he wanted $1,000 for each of the ten pictures not to be posted online.

Deputy Public Prosecutor Eunice Lau said Rafee demanded Mr Zayed pay him by 10pm that day.

When he did not receive a cent, Rafee accused Mr Zayed of cheating and posted a video showing Mr Omar and his fiancee embracing and kissing on YouTube, then forwarded him a link to the clip.

The fiancee told her husband-to-be what had happened and he lodged a police report,

Rafee, whose contract was terminated by his taxi company, was arrested at his home in Bedok Reservoir Road the next day. He is out on bail of $20,000.

The maximum penalty for criminal intimidation is two years' jail and a fine.