The US ambassador to Libya and three other embassy staff have been killed by protesters angry about an American film deemed blasphemous to the Prophet Mohamed.

52-year-old Chris Stevens died of smoke inhalation while trying to evacuate staff from the US consulate in Beghazi after protesters stormed the compound and killed Sean Smith - a foreign service information management officer.

In the subsequent chaos, the protesters fired rockets at the vehicle Mr Stevens was escaping in, disabling it.

It is thought two unidentified Marines attempted to drag the ambassador from the burning car, before being shot dead by the mob themselves.

Graphic images from the scene show civilians then taking over the rescue operation, but their efforts to save Mr Stevens’ life proved futile.

US President Barack Obama condemned the attack, ordering increased security at US diplomatic posts around the world.

The assault followed a protest in neighbouring Egypt where around 2,000 demonstrators scaled the walls of the US embassy before ripping down and burning the American flag and replacing it with a banner associated with ultraconservative Islam.

The attacks are in protest at the release of a 14-minute long trailer for a US-made film that ridicules Prophet Mohamed.

The film, titled The Innocence of the Muslims, depicts Mohamed as a fraudulent womaniser who demands massacres.

It was made by 56-year-old filmmaker Sam Bacille, who identifies himself as an Israeli Jew and in an interview yesterday said: “Islam is a cancer, period”.

Mr Bacille is now reported to be in hiding, fearing for his life.

Originally filmed in English, the trailer was later translated into Egyptian Arabic.

It has featured in Egyptian media reports for several days, with many conservative clerics publicly denouncing it.

Matters came to a head yesterday when hundreds of protests descended on downtown Cairo, gathering outside the walls of the US embassy.

Most of the embassy staff had already evacuated the building amid warnings of the demonstration, but that didn’t stop protesters, some of whom were wearing masks and chanting pro al-Qa’ida messages, scaling the walls and spraying religious graffiti.

The protests, which took place on the 11th anniversary of the September 11th attacks in New York, then spread to Libya where a group calling themselves the Islamic Law Supporters launched an attack on the US consulate in Beghazi.

In a personal statement on the attacks, US President Obama paid tribute to Ambassador Stevens, calling him a “a courageous and exemplary representative of the United States”.