A number of Russian cruise missiles launched at Syria crashed in Iran instead, U.S. officials told CNN Thursday.

U.S. intelligence has concluded that at least four missiles crashed en route to targets in Syria. One official said there might be casualties.

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Russia launched cruise missiles from its warships in the Caspian Sea into the country for the first time on Wednesday, an escalation of its military campaign to shore up its ally, Syrian President Bashar Assad.

The cruise missiles have to fly through Iranian and Iraqi airspace before landing in Syria. It's unclear where in Iran the missiles landed.

Defense Secretary Ash Carter admonished Russia on Thursday for its "increasingly unprofessional behavior."

The Pentagon on Wednesday said that at least once U.S. aircraft have had to change course to avoid colliding with Russian planes, which began bombing targets in Syria last week.

It also said Russia gave no warning of its missile launch on Wednesday, which could threaten U.S. and coalition aircraft operating in Iraqi airspace.

Last weekend, the North Atlantic Treaty Organization (NATO) and Turkey said Russian aircraft had violated Turkish airspace twice.

The U.S. and Russia last week began a first round of military talks to discuss avoiding midair collisions, but a second round has not yet been scheduled.

During the first session, the U.S. presented Russia with a plan to avoid accidents in airspace, but defense officials say Russia has not yet responded. The U.S. has urged Russia to focus its attacks on the Islamic State in Iraq and Syria (ISIS) and not rebel groups also fighting against Assad.

The U.S. has left open the possibility of cooperating with Russia if it limits its attacks to ISIS only.

"We have not and will not agree to cooperate with Russia so long as they continue to pursue this misguided strategy," Carter said earlier this week.

"It remains our hope that Russia will see that tethering itself to a sinking ship is a losing strategy because Russia has the opportunity to change course and do the right thing. I don't know if they will."

The U.S. in the meantime, said it will continue its military campaign in Iraq and Syria against ISIS.

On Thursday, Rep. Ed Royce (R-Calif.), the House Foreign Affairs Committee chairman, called on the administration to respond to Russia's actions in Syria.

“Putin has taken more action in two weeks in Syria than Obama has in two years," Royce said in reference to Russian President Vladimir Putin.

"The Russians are quickly undermining U.S. influence in the region and even violating NATO’s airspace by freely overflying Turkey. And all of this being planned and coordinated with Iran," he added.

"U.S. partners in the region are dismayed. Our Defense Secretary is criticizing the Russian strategy, but where is ours? The American people, Congress, and our allies are waiting. Brutalized Syrians are waiting.”