LOS ANGELES (Reuters Life!) - Thriller “Unknown” topped box office charts over a long U.S. holiday weekend that saw several movies bunched near $20 million, including adventure “I Am Number Four,” according to studio estimates Sunday.

“Unknown,” starring Liam Neeson as a man who must reclaim his identity after finding it stolen when he awakens from a coma, earned $21.8 million for its distributor Warner Bros. to claim the No. 1 spot at U.S. and Canadian box offices.

Also in its first weekend in theaters, science fiction action flick “I Am Number Four” landed at No. 2 with $19.5 million in a near tie with animated family film “Gnomeo and Juliet,” which earned $19.4 million for a scant drop of only 23 percent from last weekend.

Both those films were released by Disney studios.

Ticket sales estimates could change as the U.S. is in the middle of a long holiday weekend for Monday’s Presidents Day holiday. Warner Bros. is a unit of Time Warner Inc. and Disney is part of The Walt Disney Co.