LONDON, Sept. 6 (Xinhua) -- Cristiano Ronaldo scored a hat- trick as Portugal fought back from behind to beat Northern Ireland 4-2 in their World Cup Group F qualifier at Windsor Park, Northern Ireland, on Friday.

Bruno Alves put the visitors ahead after 21 minutes with a volley following Joao Moutinho's corner but Gareth McAuley headed Northern Ireland leveler 15 minutes later from a Shane Ferguson corner, the Skysports reported.

Helder Postiga was then sent off just before the break and the hosts made Portugal pay when Jamie Ward scored from a corner soon after the restart.

Chris Brunt was sent off for a second bookable offence and Portugal took advantage, with Ronaldo heading home goals in 68 and 77 minutes.

Substitute Kyle Lafferty was also given his marching orders in 80 minutes for a late challenge and Ronaldo completed his hat- trick three minutes later to make sure of the points and send his side back to the top of Group F, while Northern Ireland remain in fourth.