David Jefferies was a star rider at the Isle of Man TT races

Isle of Man TT star David Jefferies has been killed in an accident during a practice session for this year's races.

Fellow rider Jim Moodie was seriously injured in the same incident, which happened on a fast stretch of the circuit near the village of Crosby.

Jefferies, who was 30, was one of the most successful racers on the island's Mountain Course.

He had been entered in four races at this year's TT, riding for the TAS Suzuki team and was gunning for a fourth consecutive treble.

Jefferies was the outright lap record holder at the TT and had lapped at 125mph on his first lap on Thursday riding his 1,000cc Temple Auto Salvage GSXR Suzuki.

The organisers said they have launched an inquiry into the details of the incident.

The TT is notoriously dangerous and riders are regularly killed as they test the limits of themselves and their bikes.

Jefferies was a popular figure in Northern Ireland where he won four races at the North-West 200 and four at the Ulster Grand Prix.