Islamic militants in Iraq overran the city of Mosul on Tuesday, gaining control of Nineveh   provincial headquarters, the airport, two television stations and other facilities, authorities said.

The militants, who were affiliated with the Al Qaeda splinter group Islamic State of Iraq and Syria, reportedly took control of most of the nation’s second-largest city after a four-hour battle with security forces. Past fighting had not resulted in the collapse of security forces that  followed the battle Monday night and Tuesday.

Prime Minister Nouri Maliki called for parliament to declare a state of emergency and urged international organizations such as the United Nations, the Arab League and the European Union to support Iraq's mission in “combating terrorism.” The attack was seen as a bid by militants to expand their influence in Iraq and neighboring Syria, officials said.

Atheel Nujaifi, the Mosul-born governor of Nineveh province and brother of the speaker of parliament, released a statement from an unknown location after fleeing the attack. He called on “the people of Mosul to be steadfast in their neighborhoods” and to form local militias, or “popular committees,” in cooperation with the security organizations in the province.

Activists using social media posted pictures of long lines of cars and people presumably escaping Mosul, while broadcast stations associated with the Islamic State of Iraq and Syria showed video of residents “ecstatically greeting their brothers from the Islamic State.” Some Mosul residents mocked security forces who abandoned their posts.

Maliki’s Shiite Muslim-led government faces significant challenges in Mosul, which has a Sunni Muslim majority. Al Qaeda-linked militants and other extremists this year also overran the strategic city of Fallouja.

The extremist Islamic State of Iraq, the Al Qaeda affiliate responsible for much of the sectarian insurgency against U.S. forces in the 2003 invasion of Iraq, expanded into neighboring Syria after the antigovernment uprising that began in March 2011, filling what Robert Ford, a former U.S. ambassador to Syria, called “an ungoverned space” that has become a haven for extremists.

The group's takeover of Mosul was met with fear by some residents in Syrian cities near the Iraqi border, including Dair Alzour and Hasakah.

“The southern and eastern parts of Hasakah are in the hands of ISIS, and the Iraqi side is an open border not under the control of the Iraqi army,” said Al-Haskawi Al-Amir, a media activist contacted via Skype. “So today this is a consolidation of ISIS' control in Iraq and Syria.”

Bulos is a special correspondent.