Tony Frost and Dominic Ostler struck centuries for Warwickshire as desperate Yorkshire struggled on the opening day at Edgbaston.

The defending champions need to win to stand a chance of staying in Division One, but their task looks a tough one after the Bears reached 374 for five at stumps.

Frost made 103, his first ton in the Championship, while Ostler was 126 not out after striking 24 boundaries in an excellent knock that looks far from over.

Mark Wagh was an early casualty, bowled by Steve Kirby for two after the hosts won the toss and batted.

The loss was covered by a 140-run stand for the second wicket between skipper Mike Powell and Frost, the former falling lbw to Ryan Sidebottom for 58.

Ian Bell's disappointing season continues, and he soon followed Powell back to the dressing room when removed by rookie Nick Thornicroft for 15.

No sooner had Frost celebrated his milestone than he fell lbw to Anthony McGrath for 103, a 158-ball innings that included 15 fours.

Dougie Brown then played second fiddle in a 112-run stand with Ostler before falling to Sidebottom for 28.

Warwickshire: M J Powell (Capt), M A Wagh, I R Bell, D P Ostler, D R Brown, T Frost, K J Piper (Wkt), M A Sheikh, N M Carter, A Richardson, J A S Spires.

Yorkshire: V J Craven, C White, M T G Elliott, A McGrath, M J Lumb, G M Fellows, N D Thornicroft, R J Blakey (Capt, Wkt), R K J Dawson, R J Sidebottom, S P Kirby.

Umpires: P Willey and V A Holder