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Bullit Marquez, Associated Press
In this April 12, 2013, file photo, a U.S. Marine F/A-18 Hornet jet flies low pass during Philippines-US joint military exercise in northern Philippines. President Barack Obama authorized U.S. airstrikes in northern Iraq, Thursday, Aug. 7, 2014, warning they would be launched if needed to defend Americans from advancing Islamic militants and protect civilians under siege.

IRBIL, Iraq — Iraqis on Friday welcomed the U.S. airlift of emergency aid to thousands of people who fled to the mountains to escape Islamic extremists and called for greater intervention, as U.S. warplanes struck the militants for the first time.

Cargo planes dropped parachuted crates of food and water over an area in the mountains outside Sinjar near the Syrian border, where thousands of members of the Yazidi minority where sheltering, according to witnesses in the militant-held town, who asked not to be identified for security reasons.

The airstrikes were meanwhile launched outside the Kurdish regional capital Irbil, and marked the first time U.S. forces have directly targeted the extremist Islamic State group, which controls large areas of Syria and Iraq.

In contrast to Washington's decision to invade Iraq more than a decade ago, both the airdrop and the authorization of military action against the Islamic State group were widely welcomed by Iraqi and Kurdish officials fearful of the militants' lightning advance across the country.

"We thank Barack Obama," said Khalid Jamal Alber, from the Religious Affairs Ministry in the semi-autonomous Kurdish government in northern Iraq.

The Iraqi Ministry of Immigration and the Displaced also welcomed the aid drops. Ministry spokesman Satar Nawrouz said the drops came "just in time."

After seizing Iraq's second largest city Mosul in June, the Islamic State group advanced across the north, pushing back Kurdish forces and coming within 40 miles (60 kilometers) of Irbil.

On Friday the Pentagon said U.S. fighter jets had dropped 500-pound bombs on a piece of artillery and a truck towing it after it fired near U.S. personnel outside the city.

Iraqi Kurdish lawmaker, Ala Talabani said that a real U.S. military help is badly needed now after the recent gains by the militants who were able to overcome both the Iraqi army and Kurdish peshmerga forces.

"What the Iraqi people need from the United States is strong and aggressive airstrikes instead of limited ones because the situation is very delicate and cannot be solved with limited actions," he said.

The extremist group's capture of a string of towns and villages in the north has sent minority communities fleeing for their lives. The Islamic state views Yazidis and Shiite Muslims as apostates, and has demanded Christians either convert to Islam or pay a special tax.

About 50,000 Yazidis — half of them children, according to U.N. figures — fled to the mountains outside Sinjar where they were running out of food and water.

An Iraqi military handout video posted online showed Iraqi troops in helicopters delivering aid to the area. The footage corresponds to AP reporting of events.

Traveling in India, Defense Secretary Chuck Hagel said earlier Friday that if Islamic militants threaten U.S. interests in Iraq or the thousands of refugees in the mountains, the U.S. military has enough intelligence to clearly single out the attackers and launch effective airstrikes.

He also told reporters that more than 60 of the 72 bundles of food and water airdropped onto the mountain reached the people stranded there.

The rush of people expelled from their homes or fleeing violence has exacerbated Iraq's already-dire humanitarian crisis, with some 200,000 Iraqis joining the 1.5 million people already displaced from violence this year.

A representative of Iraq's most influential Shiite cleric, Grand Ayatollah Ali al-Sistani, called for a more comprehensive international intervention to support the Iraqi government.

"The statements of condemnation or consolation in support of the affected people or just sending humanitarian aid are not enough. Rather, solid plans, in cooperation with the Iraqi government, should be put in place to confront and eliminate the terrorists," said al-Sistani's spokesman Abdul-Mahdi al-Karbalaie in his Friday sermon in the holy city of Karbala.

Obama's announcement on Thursday reflects the deepest American engagement in Iraq since U.S. troops withdrew in late 2011, after nearly a decade of war.

The decision appears to have been driven by fears of an impending as well as the longstanding U.S. ties with Iraq's Kurds, which go back to the first Gulf War in the 1990s.

Washington has been more hesitant to intervene on behalf of the central government in Baghdad. Prime Minister Nouri al-Maliki has been widely blamed for the crisis, with critics accusing him of monopolizing power and pursuing a sectarian agenda that excluded Sunnis and Kurds.

The Islamic State group, which has carved out a self-styled caliphate across wide swaths of Syria and Iraq, seized Iraq's largest hydroelectric dam on Thursday, taking control of enormous power and water resources and leverage over the Tigris River that runs through the heart of Baghdad.

On Thursday the group said it has seized 17 Iraqi cities, towns and targets — including the dam and a military base — over the past five days, including Qaraqoush, the largest Christian village in Iraq.

An Iraqi government official, speaking on condition of anonymity because he was not authorized to talk to media, confirmed the takeover of the dam and described the situation as "very dangerous."

In Irbil, about 3,000 Christians who fled their homes in Qaraqoush huddled inside St. Joseph's cathedral. They said they were happy about the possibility of American airstrikes.

"We are pleased with the airstrikes and we hope we can go back to our properties," said one of the Qaraqoush refugees, 43-year-old Luay Janan.

Meanwhile, the Islamic State extremist group claimed responsibility for a deadly attack in northern Baghdad that killed 17 people late Thursday. In a statement posted Friday on a militant website frequently used by the group, it said that the attack was a double suicide bombing.

Yacoub reported from Baghdad. Associated Press writer Vivian Salama in Baghdad, Qassim Abdul-Zahra in Boston and Lolita Baldor in New Delhi contributed to this report.