Cristiano Ronaldo's late header helped Portugal into the semi-finals of the European Championships with a hard-fought 1-0 win over the Czech Republic in Warsaw.

The Real Madrid forward twice hit the woodwork and saw his side have a goal chalked out for offside.

But he arrived on cue in the six-yard box to nod in Joao Moutinho's cross on 79 minutes, and ensure a last-four meeting with either Spain or France.

The Czechs - with captain Tomas Rosicky, the Arsenal midfielder, only on the bench because of an Achilles injury - had started brightly, but lacked a decisive move in the final third. It had been a decent opening from Michal Bilek's side as Petr Jiracek drilled the ball in from 20 yards, but his effort was blocked by Real Madrid defender Pepe.

On 17 minutes, the Czech Republic, who overcame a 4-1 defeat in their opening game against Russia to win Group A, broke quickly down the right and Vladimir Darida whipped over a low cross through the six-yard box, which Galatasaray striker Milan Baros just failed to connect with.

Portugal were forced into a change six minutes before half-time when striker Helder Postiga pulled up with what appeared to be a hamstring problem, and was replaced by Hugo Almeida.

Portugal continued to press and Ronaldo was within inches of a spectacular opening goal when he collected a high ball into the box on his chest, swivelled around marker Kadlec and crashed the ball past Cech - only for it to strike the base of the near post.

There was another great chance for Portugal at the start of the second half, when Almeida headed over from 12 yards after being picked out by Raul Meireles' cross. On 50 minutes, Ronaldo was denied by the woodwork again as this time his 30-yard free-kick clipped the outside of the far post with Cech beaten.

The Chelsea keeper then had to parry away a 25-yard strike from Nani, and only an offside flag prevented Portugal taking a deserved lead on 57 minutes when Almeida glanced in the United winger's cross.

Ronaldo finally broke the deadlock on 79 minutes, when he sent a diving header past Cech from Moutinho's right-wing cross. Portugal continued to pour forward - with Cech beating away an angled 25-yard effort from full-back Joao Pereira - but were able to see out stoppage time for the win.