Peter Trego's blistering innings of 79 and some astute bowling by Alfonso Thomas gave Somerset their first Twenty20 Cup success this season.

Somerset scored 185-6 after losing the toss, with Trego hitting seven fours and three sixes in his 50-ball innings.

The Sabres restricted Glamorgan to 170-5 for five, despite 76 not out off 51 balls from Herschelle Gibbs.

Seamer Thomas took 1-21 from his four overs as the home side held on for a 15-run victory at Taunton.

Arul Suppiah also weighed in with useful left-arm spin, conceding 27 from four overs.

South African Gibbs hit nine fours and two sixes in a superb exhibition of hitting, while Robert Croft also played well for his 50 off 37 balls.

The duo took the score to 117-1 in the 13th over before Thomas had Croft caught at backward point with a slower ball.

And Glamorgan gradually lost their way in failing light, with Thomas running out Mike Powell, while Mark Turner picked up two wickets in the final over to seal the visitors' fate.

Earlier, Somerset lost Marcus Trescothick to the second ball of the match.

The former England opener was caught behind swinging at a good length ball from Harrison.

Justin Langer then skied a catch to Jamie Dalrymple at mid-wicket, before Trego took centre stage.

Wicketkeeper Craig Kieswetter helped Trego add 59, scoring his 42 runs off 26 balls, with three fours and two sixes, the latter coming off successive balls from Ryan Watkins in the 17th over.