At least 15 people have been killed in Pakistan in clashes during protests over an anti-Muslim film.
Police fired tear gas and live ammunition at thousands of demonstrators who threw rocks and set fire to buildings. Dozens were injured.
Muslims also marched in at least a half-dozen other countries, with some burning American flags and effigies of US President Barack Obama.
Pakistan has experienced nearly a week of deadly protests over the film, Innocence of Muslims, that has sparked anti-American violence around the Islamic world since it emerged on the internet in the past 10 days.
The deaths of at least 45 people, including the US ambassador to Libya, have been linked to the violence over the film, which was made in California and denigrates the Prophet Mohammed.
The Pakistani government declared yesterday to be a national holiday – “Love for the Prophet Day” – and encouraged peaceful protests.
The US Embassy spent $70,000 (£43,000) for advertisements on Pakistani TV that featured Mr Obama and Secretary of State Hillary Clinton denouncing the video.
The deadliest violence occurred in the southern port city of Karachi, where 12 people were killed and 82 wounded, according to hospital officials. Armed demonstrators among a crowd of 15,000 fired on police, authorities said. The crowd also burned two cinemas and a bank.
Three people were killed and 61 wounded in the north-western city of Peshawar, where police fired on rioters.
Police beat demonstrators with batons. Later in the day, tens of thousands of protesters converged in a neighbourhood and called for the maker of the film, an American citizen originally from Egypt, to be executed.
Police and stone-throwers also clashed in Lahore and Islamabad, the capital.
The government temporarily blocked mobile phone service in 15 major cities to prevent militants from using phones to detonate bombs during the protests.
Pakistan’s Foreign Ministry summoned the US envoy in Islamabad, Richard Hoagland, over the film.
Pakistan has banned access to YouTube because the website refused to remove the video.
Pakistani Prime Minister Raja Pervaiz Ashraf had urged the international community to pass laws to prevent people from insulting the prophet.
“If denying the Holocaust is a crime, then is it not fair and legitimate for a Muslim to demand that denigrating and demeaning Islam’s holiest personality is no less than a crime?” Mr Ashraf said in a speech to religious scholars and international diplomats in Islamabad.
US officials say they strongly disagree with the anti-Islam film but have no ability to block it because of free speech guarantees.
In Iraq, about 3,000 protesters condemned the film and caricatures of the prophet that were published in a French satirical weekly.
In the Sri Lanka capital of Colombo, about 2,000 Muslims burned effigies of Mr Obama and US and French flags.
Thousands gathered in Lebanon’s Bekaa Valley for the latest in a series of rallies organised by the Shi’ite militant group Hezbollah. Protesters carried the yellow Hezbollah flag.