Cloverfield is seen as if through the lens of a hand-held video camera

The film, which stars previously unknown actors, follows a group of young New Yorkers on the night a giant monster attacks the city.

It took �3.5m in ticket sales, beating musical Sweeney Todd: The Demon Barber - which took �1.7m over the weekend - into second place.

Eva Longoria comedy Over Her Dead Body was third on its opening weekend.

UK AND IRELAND BOX OFFICE 1. Cloverfield - �3.49m 2. Sweeney Todd - �1.71m 3. Over Her Dead Body - �996,000 4. Penelope - �770,000 5. No Country For Old Men - �712,000 Source: Screen International

The Desperate Housewives star's character dies on the day of her wedding before coming back to haunt his fiance's new girlfriend.

Modern romantic fairytale Penelope, starring Christina Ricci and also on its opening weekend - was fourth.

The Coen brothers' No Country For Old Men was fifth.

Former top film I Am Legend, starring Will Smith - which has taken �25.3m in the UK - dropped out of the top 10 for the first time.