KHAZER CAMP, Iraq (AP) -- Thousands of displaced Iraqis fled their camp in the face of advancing fighters of the Islamic State group, deepening the humanitarian crisis in the north of the country as the United States carried out its first airstrikes against the militants to blunt their assault.
The Khazer Camp stood empty Friday, located near the front lines of battles between the militants and Kurdish fighters. The camp had been populated by Iraqis who fled their cities and towns as they were taken over by Islamic State fighters in past weeks, and in the past few days they have been forced to flee again.
The militants have been making a push from their strongholds in northwest Iraq toward Irbil, the capital of the Kurdish autonomous zone. For days the two sides have been battling each other over a river at a destroyed bridge on the main road 40 kilometers (25 miles) from Irbil.
U.S. fighter jets dropped 400-pound bombs on an artillery piece and truck towing it after it fired near U.S. personnel outside Irbil, the Pentagon said.
An Associated Press reporter at Khazer saw at least six more explosions in the area Friday, apparently from airstrikes, though it was not known who was carrying them out, since the Iraqi air force has also been hitting positions of Islamic State group.
The U.S. airstrikes and humanitarian air drops reflect the deepest American engagement in Iraq since U.S. troops withdrew in late 2011, after nearly a decade of war.
Expanding from their stronghold of Mosul, Iraq's second largest city, the militants have captured a string of surrounding towns and even the country's largest hydroelectric dam and reservoir in recent weeks, solidifying their hold.
Ethnic and religious minorities in particular have fled in fear as their towns fall.
U.S. cargo planes on Thursday dropped relief supplies to tens of thousands of Yazidis -- half of them children, according to the U.N. -- who have been trapped on a remote desert mountain for days without food and water after militants took their town of Sinjar near the Syrian border, according to witnesses in Sinjar, who asked not to be identified for security reasons.
Yazidis belong to ancient religion seen by the Islamic State group as heretical. The group also sees Shiite Muslims as apostates, and has demanded Christians either convert to Islam or pay a special tax.
Many of the Iraqis who fled Khazer Camp in recent days made their way by car or by foot to Irbil. Others are unaccounted for amid the vast sea of refugees and internally displaced people now roaming Iraq's semi-autonomous Kurdish region.
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.
In Irbil, hundreds of displaced Iraqi men crowded the streets of a Christian-dominated neighborhood Friday, expressing relief at the news of U.S. airstrikes.
Nazar, one of the men lingering outside a bare-bones building-turned-shelter, fled his mainly Christian town of Hamdaniya on Wednesday, when their home began to shutter from the blast of nearby mortar fire.
"We want a solution," said Nazar, who spoke on condition he be identified only by his first name, fearing his family's safety. "We don't to flee our homes and jobs like this -- what is our future?"
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.
"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."
About 50,000 Yazidis are believed to have fled into the mountains outside Sinjar. An Iraqi military handout video posted online showed Iraqi troops in helicopters also delivering aid to the area. The footage corresponds to AP reporting of events.
The Islamic State group captured Mosul in June, and then launched a blitz toward the south, sweeping over Sunni-majority towns neary down to the capital, Baghdad. It already holds large parts of western Iraq, as well as large swaths of the north and east in neighboring Syria.
Iraqi government forces crumbled in the face of the assault, but have since been able to prevent the militants from advancing into Shiite-majority areas. In the north, the Kurds have been the main line of defense against the radicals, but their fighters are now stretched over a long front trying to fend them off.
Now it is expanding in the north. 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. The group also claimed responsibility for a deadly attack in 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.
Iraqi Kurdish lawmaker, Ala Talabani said that a real U.S. military help is badly needed now.
"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.
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.
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.
Associated Press writers Sameer N. Yacoub and Vivian Salama in Baghdad, Qassim Abdul-Zahra in Boston and Lolita Baldor in New Delhi contributed to this report.