"I don't want to talk about what happened in other countries but as for Libya, the operation was meticulously executed," Mohammed al-Megaryef,  the country's assembly chief, said on Saturday of the wave of protests across the world over a US-produced film mocking Islam.

"There was planning. It was not a peaceful protest which degenerated into an armed attack or aggression. That's how it was planned," he said.

US ambassador Chris Stevens and three other Americans were killed on Tuesday when suspected Islamic militants fired on the consulate in the eastern Libyan city with rocket-propelled grenades and set it ablaze.