By Michelle Nichols
UNITED NATIONS, July 23 (Reuters) - The U.N. special envoy to Iraq urged the United Nations Security Council on Wednesday to demand an end to "hostilities and atrocities" committed by Sunni Islamist militants, saying the insurgents pose a threat that "is not and will not be limited to Iraq."
The advance by al Qaeda offshoot Islamic State, known as the Islamic State in Iraq and the Levant (ISIL) when it seized swaths of northern Iraq last month, has put the OPEC oil producer's survival in jeopardy.
The group now controls territory stretching from Aleppo in Syria, close to the Mediterranean, to the outskirts of Baghdad.
"From a splinter group of al Qaeda, ISIL has today grown to be a complex threat to peace and security in Iraq, the entire region and beyond," U.N. envoy Nickolay Mladenov told the 15-member Security Council via video link from Baghdad.
"The international community and the Security Council should demand, in no uncertain terms, that ISIL cease all hostilities and atrocities," he said. "Iraq needs and must receive regional and international support."
Mladenov reiterated U.N. Secretary-General Ban Ki-moon's push for countries to enforce an international arms embargo and economic sanctions on the Islamic State militant group in a bid to weaken the insurgency.
Al Qaeda in Iraq was blacklisted by the Security Council a decade ago and that designation was amended last year to include ISIL. The group follows al Qaeda's hardline ideology, but alienated Osama bin Laden's successor Ayman al-Zawahri and others with its extreme violence.
Mladenov also called on countries to "hold accountable the perpetrators, organizers and sponsors of these horrific terrorist acts, war crimes and crimes against humanity."
The U.N. has accused Islamic State fighters of executions, rape and forced recruitment of children during its campaign to seize much of northern Iraq.
Mladenov said almost 900 people had been killed during the violence in July alone, while some 5,500 people died between January and June.
"We have received reports of women being targeted and having severe restrictions placed on their freedoms," he said. "I am also alarmed by the killing and maiming of children due to indiscriminate attacks ... and the ongoing recruitment and use of children, as young as 12, but all parties."
Iraq's parliament, which had been due to elect the country's president on Wednesday, postponed the vote by a day, delaying the formation of a power-sharing government urgently needed to confront the insurgency.
"Iraq cannot afford a protracted government formation process as the current threats continue to challenge the existence of the Iraqi state," Mladenov said.
(Reporting by Michelle Nichols; Editing by Tom Brown)