Fresh protests have erupted across the Islamic world, sparked by the Internet video that mocks the Prophet Muhammad.

In Pakistan, protests turned violent in the capital, Islamabad, and in Karachi and Peshawar. At least 13 people were killed in clashes between security personnel and protesters, including a policeman in Karachi.

Pakistan's Foreign Ministry says it summoned U.S. diplomat Richard Hoagland to register a “strong protest” over the film. Hoagland reiterated U.S. condemnation of the video and emphasized the U.S. government had nothing to do with it.

Pakistan's government designated Friday to be a national holiday and “a day of love for the Prophet Muhammad.”

Thousands of Muslims also protested in other countries, including Afghanistan, India, Sri Lanka, Bangladesh, Iraq, Lebanon and Indonesia. Some protesters burned American flags and effigies of U.S. President Barack Obama.

U.S. embassies across the Islamic world remain on high alert for protests.

Pakistani media said the government called on the army to protect Islamabad's diplomatic enclave, where 15,000 people were expected to march.

Cell phone service was blocked in 15 Pakistani cities, including Islamabad and the eastern city of Lahore.

The low-budget Internet video was produced by an anti-Muslim filmmaker in California. It first sparked protests last week in Cairo and the Libyan city of Benghazi, where U.S. Ambassador J. Christopher Stevens and three other embassy personnel were killed. Since then, anti-U.S. protests have spread as far as Indonesia.

The U.S. embassy in Pakistan is airing a public service advertisement on Pakistani television that features President Obama denouncing the video.

Pakistani Prime Minister Raja Pervez Ashraf told a conference of religious leaders and politicians in Islamabad that Pakistan is demanding the United Nations and other international organizations seek a law that bans “such hate speech, equal to the worst kind of anti-Semitism or other kinds of bigotry.”

In France, the government said it is closing its embassies, consulates, cultural centers and schools in 20 countries Friday as a precautionary measure. French authorities also banned two anti-U.S. protests planned for Saturday.

The French weekly Charlie Hebdo featured several images of the Prophet Muhammad in its Wednesday issue, including several of him naked.