In a huge blow to Iranian interest, the radical Sunni group the Islamic State of Iraq an al-Sham seized the Iraqi city of Mosul.

BEIRUT — Insurgents seized control early Tuesday of most of the northern Iraqi city of Mosul, including the provincial government headquarters, offering a powerful demonstration of the mounting threat posed by extremists to Iraq’s teetering stability.

Fighters with the Islamic State of Iraq and Syria (ISIS), an al-Qaeda offshoot, overran the entire western bank of the city overnight after Iraqi soldiers and police apparently fled their posts, in some instances discarding their uniforms as they sought to escape the advance of the militants.

Iraq’s speaker of parliament, Osama Nujaifi, said the city that ranks as the capital of northern Iraq is now entirely in insurgent hands.

Let these savages kill each other.