Speaking on the sidelines of a NATO foreign ministers meeting in Brussels, she said Israel needed to respect international law. Seven aid workers died in the attack on Monday, including 33-year-old dual U.S.-Canadian citizen Jacob Flickinger.

In Toronto, Prime Minister Justin Trudeau said officials had spoken to Israeli ambassador Iddo Moed to express "our dismay at the unacceptable deaths of a Canadian-American aid worker along with others ... the world needs very clear answers as to how this happened".

Israel says the air strike that killed the seven aid workers was a mistake.

(Reporting by John Irish in Brussels and David Ljunggren in Ottawa; Writing Benoit Van Overstraeten; Editing by GV De Clercq and Chizu Nomiyama)