The U.S. military has begun a second round of airstrikes against ISIS near Irbil, U.S. officials told CNN on Friday.

News of the latest airstrikes came just after the governor of Irbil, Nawzad Hadi, told CNN, that ISIS fighters may be as close as 30 kilometers to Irbil. Air strikes are “very important” because ISIS fighters are well armed and are outgunning the Kurdish forces, thanks to the weapons the militants seized from the Iraqi military in Mosul, Hadi said.

During that second airstrike, four U.S. fighter jets struck an ISIS convoy of seven vehicles, Pentagon spokesman Rear Adm. John Kirby said.

The warplanes dropped four laser-guided bombs, he said.

[Original story published at 2:49 p.m.]

U.S. jet fighters strike ISIS in Iraq

Two U.S. F/A-18 jet fighters bombed artillery of Sunni Islamic extremists in Iraq on Friday, escalating America’s military involvement more than two years after President Barack Obama brought home forces from the country.

Obama on Thursday authorized “targeted airstrikes” if needed to protect U.S. personnel from fighters with ISIS, which calls itself the Islamic State. The U.S. military also could use airstrikes to prevent what officials warn could be a genocide of minority groups by the ISIS fighters.

Though the United States is supporting Iraq militarily, there won’t be U.S. combat troops on the ground, and it ultimately will be up to the Iraqi government and security forces to resolve the ISIS threat, White House spokesman Josh Earnest told reporters Friday.

“There will not be American troops returning to Iraq in a combat role,” he said, repeating what Obama said in an address Thursday night.

“As commander in chief, I will not allow the United States to be dragged into fighting another war in Iraq,” the President said.

Meanwhile, a senior Kurdish official told CNN that ISIS militants captured Iraq’s largest hydroelectric dam, just north of Mosul, Iraq’s second-largest city. According to the official, the militant fighters have been using U.S.-made weapons seized from the Iraqi army, including M1 Abrams tanks.

There had been conflicting reports about who controlled the dam on the Tigris River, with heavy fighting under way between ISIS fighters and Kurdish forces, known as Peshmerga. U.S. officials have warned that a failure of the dam would catastrophic, resulting in flooding all the way to Baghdad.

In other fighting, an Iraqi airstrike killed 45 ISIS fighters and injured 60 Friday in the northern town of Sinjar, the country’s state-run National Media Center said.

Sinjar is the town that ISIS raided last weekend, causing members of the Yazidi minority there to flee into surrounding mountains without food, water or shelter and prompting concerns of a potential genocide. The Yazidis are of Kurdish descent, and their religion is considered a pre-Islamic sect that draws from Christianity, Judaism and Zoroastrianism.

U.S. flights prohibited

Other signs of a growing regional conflict: The Federal Aviation Administration issued a notice prohibiting U.S. airlines from flying through Iraqi airspace “due to the hazardous situation created by the armed conflict.”

The developments showed that the lightning advance by ISIS fighters across northern Iraq this year has become a battle for the nation’s future and overall stability in a part of the world wracked for decades by periodic war.

French President François Hollande strongly condemned ISIS attacks against the Iraqi population and vulnerable minorities such as Yazidis and Christians and called for the international community to respond.

“France is ready to take its part,” Hollande said in a statement from his office that called for the European Union “to take an active role very quickly” and put in place all the necessary assistance to respond to the crisis.

U.S. warplanes patrolling the skies over northern Iraq have a “green light” to go after perceived ISIS threats to the Kurdish capital, Irbil, or to minority populations, said deputy national security adviser Ben Rhodes.

Airstrikes are also possible to help Kurdish forces end the siege by ISIS in the northern Iraqi mountains, where tens of thousands of Yazidis have sought refuge, Earnest, the White House spokesman, said Friday.

ISIS fighters have surrounded the Yazidis on the ground below.