At least three people have been killed and dozens injured in clashes between Pakistani police and protesters over the low-budget US film "The Innocence of Muslims" that has sparked riots across the Islamic world.

Angry demonstrators set fire to two cinemas in the northwestern city of Peshawar, DawnNews reported.

Western diplomatic missions throughout the Muslim world have stepped up security arrangements, some closing down in anticipation of massive protests after Friday prayers.

The Innocence of Muslims, an amateurish US-produced video that denigrates the Prophet Muhammad, has sparked widespread protests across the Middle East and North Africa, some of which have turned violent.

US Ambassador to Libya Chris Stephens and three embassy staff were killed during an attack on the US consulate in the Libyan city of Benghazi earlier this month.

"An attack upon the Holy Prophet is an attack on the whole 1.5 billion Muslims. Therefore, this is something unacceptable," Pakistani Prime Minister Raja Pervez Ashraf said.

Pakistan has declared Friday a "Day of Love for the Prophet Mohammad."

Meanwhile, a US actress who appeared in the film has sued its producer for fraud and slander, claiming the script she was given made no mention of the Prophet Muhammad, RIA Novosti reported.

Filing her lawsuit in Los Angeles on Wednesday, Cindy Lee Garcia said she was duped into acting in the "vile and reprehensible" film, which she had been told was a "historical Arabian Desert adventure film."