An armed mob protesting over a film they said offended Islam, attacked the US consulate in Benghazi on Tuesday and set fire to the building, killing one American, witnesses and officials said. Libya\'s deputy interior minister Wanis al-Sharef told AFP: \"One American official was killed and another injured in the hand. The other staff members were evacuated and are safe and sound.\" He could not say if the dead man was a diplomat. Abdelmonoem al-Horr, spokesman for the Libyan interior ministry\'s security commission, said rocket-propelled grenades were fired at the consulate from a nearby farm. Security forces and the interior ministry were trying to contain the situation, he added. The attack happened on the same day as a similar group of hardliners waving black banners attacked the US embassy in Cairo and tore down the US flag, but it was not immediately clear if the two incidents were coordinated. The protests came on the eleventh anniversary of the attacks of September 11, 2001, when US cities were targeted by hijacked planes. In Washington, State Department spokeswoman Victoria Nuland said: \"We condemn in strongest terms this attack on our diplomatic mission.\" US officials were working with the Libyans to secure the compound, Nuland said, adding that the earlier protest against the US embassy in Cairo, in which demonstrators scaled the walls, had now ended. \"Demonstrators attacked the US consulate in Benghazi. They fired shots in the air before entering the building,\" Libya\'s deputy interior minister, Wanis al-Sharif Sharif, who is in charge of the country\'s eastern region, told AFP. \"Dozens of demonstrators attacked the consulate and set fire to it,\" said a Benghazi resident, who only gave his name as Omar, adding that he had seen the flames and heard shots in the vicinity. Another Libyan witness said armed men had closed the streets leading up to the consulate, among them ultra-conservative Salafists. The Libyan incident came as thousands of Egyptian demonstrators tore down the Stars and Stripes at the US embassy in Cairo and replaced it with a black Islamic flag, similar to one adopted by several militant groups. Nearly 3,000 demonstrators gathered at the embassy in protest over a film deemed offensive to the Prophet Mohammed which was produced by expatriate members of Egypt\'s Christian minority resident in the United States. Officials said it remained unclear whether the protests in Benghazi and Cairo had been coordinated or whether they were linked. \"We cannot confirm any connection between these incidents,\" said a senior State Department official, asking to remain anonymous. Muslims consider depiction of the prophet sacrilegious. Arab League deputy secretary general, Ahmed Ben Helli, has condemned the film saying it \"contained insults against the prophet Mohammed\" and \"was denounced by Christians and Muslims\" across the Arab world.