* Protests erupt in Baghdad and Basra
* PM condemns film, calls for no violence
By Suadad al-Salhy
BAGHDAD, Sept 13 (Reuters) - An Iraqi militia that carried out some of the most prominent attacks on foreigners during the Iraq war on Thursday threatened U.S. interests in the country over a film that has triggered protests in Libya, Egypt and Yemen.
"The offence caused to the messenger (Prophet Mohammad) will put all American interests in danger and we will not forgive them for that," said Qais al-Khazali, leader of the Asaib al-Haq militia.
The U.S. ambassador to Libya and three other staff were killed overnight on Tuesday in an attack on the U.S. consulate in Benghazi over the film.
Protests against the film erupted in Baghdad on Thursday and in the city of Basra, 420 km (260 miles) southeast of the capital. Hundreds of followers of anti-U.S. Shi'ite cleric Moqtada al-Sadr took to the streets calling on the Iraqi government to close the U.S. embassy.
Iraqi Prime Minister Nuri al-Maliki denounced the film as "insulting" and "racist" but called on Muslims not to react with violence.
"The natural response is to refrain from resorting to violence and demonstrate the principles of Islam and its civilised values," he said in a statement on Thursday.
In Baghdad, hundreds of protesters gathered in Sadr's stronghold of Sadr City, holding up posters of Sadr, burning U.S. flags and chanting, "Death to America".
"How long will we stay in this coma where there is no real sanction?" Sheikh Riyadh al-Waeli, a Sadr aid, told protesters. "This demonstration is not enough unless there is a real sanction."
The crowd in Basra also numbered in the hundreds and both Sunni and Shi'ite clerics participated in the demonstration, which was organised by Sadr's office.
"We have to fire the U.S ambassador because these things are carried out under U.S supervision and are aimed at offending Islam and Muslims," protester Yaarab al-Mohammadawi told Reuters.
A smaller protest also took place in the city of Najaf, 160 km (100 miles) south of Baghdad.