Defending champions Glasgow made it three wins from six matches in the new Guinness PRO12 season with a 31-19 triumph over struggling Ospreys.

The Warriors outscored their opponents four tries to one, with the hosts claiming a much-needed bonus point in the final minute through Taqele Naiyaravoro's score.

Sean Lamont, Greg Peterson and Alex Allen also crossed for Glasgow as Duncan Weir kicked 11 points, with Ospreys' response coming from Dan Baker's late try and 14 points from the boot of Wales' World Cup star Dan Biggar.

Ospreys actually led 9-8 at the interval but could not hold on as they saw both Josh Matavesi and Ryan Bevington sin binned at the start of the second period en route to a fifth defeat.

Glasgow kicked off in front of a full Scotstoun house in excellent overhead conditions and within two minutes stand-off Weir was slotting over the second of two penalties conceded by Ospreys to put his side ahead.

The visitors, for whom Scott Baldwin was a late replacement for Sam Parry at hooker, soon countered with a long-range effort from Biggar, who seven minutes later put the Welsh region in front with another kick from distance.

Glasgow settled into their standard enterprising off-loading game while Ospreys were largely content to kick for position.

On the half-hour mark, Glasgow's style finally paid off. Pressure along the Ospreys goal line ended with Fiji's Leone Nakarawa slipping the ball to Lamont who touched down for his 25th PRO12 try.

Weir, having just missed a long penalty, failed with a difficult conversion attempt but Glasgow still led 8-6.

However, Ospreys were back in front again before half-time as Biggar showed his prowess from distance once more with a booming penalty in the 37th minute, giving his side the lead going into the second half.

The lead changed hands three more times in the opening 10 minutes of the second half.

Firstly Weir struck home a penalty which was soon replicated by Biggar.

Then, in the 49th minute, referee Peter Fitzgibbon sin binned Ospreys centre Matavesi and the Warriors immediately turned up the pressure, driving a line out and finally US lock Peterson, on his starting debut, scored by the posts. Weir converted to open a Glasgow lead of 18-12.

Weir soon added another penalty and with all the play in the Ospreys' 22 visiting replacement Bevington was the next man sent to the sin bin.

Glasgow's third try was a replica of the second with substitute prop Allan getting the unconverted touch down in the 65th minute.

A breakaway try by Baker converted by Biggar seemed to have earned Ospreys a losing bonus point, but in the last act of the match Naiyaravoro grabbed Glasgow's fourth try and the extra point for the champions.