Gavin Henson secured the first try on the afternoon with wings Shane Williams and Nikki Walker also claiming Ospreys' tries, as did centre Tommy Bowe, whose injury-time effort secured a bonus point.

Fly-half James Hook kicked 17 points to deny a spirited Warriors outfit, while Hook's opposite number Matthew Jones also collected a 17-point haul from five penalties and a conversion of centre Sam Tuitupou's second-half try.

But Ospreys will win the group and secure a semi-final spot if they beat Madejski Stadium hosts London Irish next Sunday.

Worcester's New Zealand wing Rico Gear, who has scored three tries in his last two appearances for the Warriors, was a late withdrawal due to injury, so 20-year-old Charlie Fellows deputised.

Bright sunshine greeted Warriors boss Mike Ruddock on his return to Swansea - the town where he once lived and coached - as both sides targeted a victory that would keep semi-final hopes alive.

And Worcester should have taken a 10th-minute lead after absorbing early Ospreys pressure by prospering from Hook's wild pass.

He threw the ball into no-man's land just outside his 22, but Ospreys' Walker offered sufficient defensive resistance to prevent Warriors centre Alex Grove claiming a touchdown.

Despite the tournament's perceived "second-class" status, both teams went at each other in no-holds-barred fashion.

The game's admirably intense physical nature though, was overshadowed by numerous handling errors as Hook and Jones slotted early penalties.

Hook then slotted a second penalty when Matthew Jones was sin-binned on his return to the Ospreys three years after being capped by Wales from the Swansea-based region.

Worcester predictably struggled to cope with their temporary one-man disadvantage, and the Ospreys pounced for a 33rd-minute try.

A wayward kick by wing Chris Pennell put the Warriors under needless pressure, and slick Ospreys passing resulted in Walker crossing wide out.

It was the Ospreys first try in more than three hours of competitive action, and they added another during injury time after Jones rejoined the action to boot a second penalty.

Henson received the ball near halfway, then burst through a midfield hole before side-stepping Latham to claim a brilliant try.

Hook missed a second successive conversion attempt, but the Ospreys trooped off 16-6 ahead, having taken charge of the contest.

Jones' third penalty briefly cut the gap, but Worcester conceded another try with 35 minutes still remaining, as Henson and full-back Lee Byrne combined to send an unmarked Williams over.

Hook landed the touchline conversion, and despite a fourth Jones penalty, the Ospreys were in control with plenty of time to pursue a fourth-try bonus point.

The home side saw flanker Tom Smith sin-binned after a ruck offence, which provided Worcester's cue to take charge up front.

And they did not disappoint, patiently building a platform that enabled the powerful Tuitupou to plough through Ospreys' defence for a try that Jones converted.

Hook completed his penalty hat-trick to move the Ospreys 26-19 ahead, then a fourth three-pointer took Worcester out of losing bonus point range.

Hook's fourth penalty came after he was denied a try following Worcester prop Matt Mullan's superb tackle, which underlined that the Warriors had no intention of throwing the towel in.

A fifth Jones penalty reduced the gap to 29-22, but Hook struck again, before Bowe sprinted over to secure a points maximum for the Ospreys during the final seconds.

The scorers:

For the Ospreys:
Tries: Walker, Henson, S Williams, Bowe
Cons: Hook
Pens: Hook 5

For Worcester Warriors:
Tries: Tuitupou
Cons: M Jones
Pens: M Jones

The teams:

Ospreys: 15 Lee Byrne, 14 Nikki Walker, 13 Tommy Bowe, 12 Gavin Henson, 11 Shane Williams, 10 James Hook, 9 Rhys Webb, 8 Filo Tiatia, 7 Steve Tandy, 6 Tom Smith, 5 Lyndon Bateman, 4 Ian Gough, 3 Andrew Millward, 2 Huw Bennett, 1 Duncan Jones (c).
Replacements: 16 Richard Hibbard, 17 Adam Jones, 18 Alun-Wyn Jones, 19 Ryan Jones, 20 Jamie Nutbrown, 21 Dan Biggar, 22 Andrew Bishop.

Worcester Warriors: 15 Chris Latham, 14 Rico Gear, 13 Alex Grove, 12 Sam Tuitupou, 11 Chris Pennell, 10 Matthew Jones, 9 Ryan Powell, 8 Netani Talei, 7 Jake Abbott, 6 Matt Cox, 5 Craig Gillies, 4 Greg Rawlinson (c), 3 Tevita Taumoepeau, 2 Aleki Lutui, 1 Matt Mullan.
Replacements: 16 Darren Morris, 17 Shaun Ruwers, 18 Graham Kitchener, 19 Rob Wood, 20 Matt Powell, 21 Loki Crichton, 22 Charlie Fellows.

Referee: David Rose (England)
Touch judges: Chris White (England), Andrew Pearce (England)
Television match official: James Jones (England)