Police used tear gas to disperse a crowd of more than 2,000 protesters trying to reach the US consulate in northwest Pakistan on Tuesday, as fresh demonstrations erupted against an anti-Islam film.

Protesters chanting anti-US slogans and burning the Stars and Stripes flag gathered outside the mission in the city of Peshawar to vent their fury at the "Innocence of Muslims" film, which was made in America and is deemed insulting to Islam.

Around 2,000 people marched through the country's largest city, Karachi, towards the US consulate to protest against the film, which has triggered a week of deadly protests across the Muslim world.

Riot police with armoured vehicles were deployed to block access to the consulate in Peshawar, the main city in Pakistan's restive northwest, where Taliban and Al-Qaeda militants have strongholds.

"We used tear gas shells and lobbed gas grenades because the protesters were trying to come closer to the sensitive area," senior police officer Imtiaz Khan told AFP.

He said more than 1,000 police were on hand to block the road to the US consulate.

Addressing the crowd, the local leader of the hardline Sunni party Jamaat-e-Islami (JI), Shabbir Ahmed, lashed out at the United States, demanding the Pakistani government expel the American ambassador and close its missions in Pakistan.

"We are ready to sacrifice our lives to uphold the dignity of our Prophet," he said.

In the eastern city of Lahore, up to 900 people demonstrated near the US consulate, chanting "Obama is a dog" and "Death to the USA".

Some 1,500 supporters of a pro-Taliban religious party held a protest rally in the southwestern town of Chaman on the Afghan border, police and witnesses said.

The marchers, carrying banners and placards, chanted: "Down with America," and "Hang the film makers" and "Long live Mulla Omar", "Long Live Taliban and Long Live Osama bin Laden," witnesses said.

Some 1,500 people participated in the rally, local police officer Ghulam Rabbani said.

In the central city of Multan hundreds of students, traders and local power loom factory workers carried out separate rallies, police and residents said.

They blocked roads by burning tyres, and torched US flags and the effigy of the producer of the anti-Islam film, police said.

A similar rally was held in the industrial city of Faisalabad.

The protest came after a female suicide bomber killed 12 people in Kabul on Tuesday in an attack claimed by an insurgent group as revenge for the film.

The blast brought the total number killed in a week-long violent backlash against over the film to 30.

There have been furious protests outside US embassies and other American symbols in at least 20 countries, with the American ambassador to Libya and three other US diplomats in the North African country among those killed.

In Pakistan two protesters died after demonstrating against the film in the northwest, close to the Afghan border, and outside the US consulate in Karachi.

Afghanistan, Bangladesh and Pakistan have all blocked access to YouTube, following the video-sharing website's failure to take