Trudeau and his three counterparts, whose countries together with the U.S. are part of the tightly knit Five Eyes intelligence alliance, have gathered in London for this week's summit of Commonwealth leaders.

Security and justice officials from the Five Eyes countries plan to explore "more timely and detailed" information sharing to detect terrorists and extremist fighters.

Civil libertarians argue the right of law-abiding people to communicate in private should not be sacrificed in the name of fighting terrorism.