The U.S., along with Arab allies, carried out a series of attacks Tuesday on the Islamic State in Syria. Video posted to social media purports to show the aftermath of those airstrikes. (The Washington Post)

Syria was informed by the United States in advance of airstrikes against targets including Islamic State strongholds, but there was no strategic coordination with the Syrian government, a State Department spokeswoman said Tuesday.

Although the United States said it gave no specifics on the attacks and did not request clearance from Damascus, it marked a rare display of interaction between Washington and envoys for Syrian President Bashar al-Assad.

“We warned Syria not to engage U.S. aircraft,” said State Department spokeswoman Jen Psaki in Washington. “We did not request the regime’s permission. We did not coordinate our actions with the Syrian government.”

The Pentagon said separately Tuesday that there was no “military-to-military” communication with Syrian government forces but that they appeared to get the message not to interfere with the airstrikes. Army Lt. Gen. William C. Mayville Jr., the Pentagon’s director for operations, described Syrian military radar as “passive” during the strikes, with no attempt to counter them.

Psaki said U.S. officials provided no details about the timing or targets in the U.S.-led airstrikes, which included support from Arab nations opposed to Assad such Qatar and Saudi Arabia.

Maps: U.S.-led airstrikes in Syria.

But the outreach suggests a small but important shift by the United States and its allies, which have given diplomatic and limited military support to rebels seeking to overthrow Assad.

The expansion of U.S.-led airstrikes into Syria could now open new channels to Assad’s government, which last year faced possible Western air attacks over the Syrian military’s reported use of chemical weapons against civilians in rebel-controlled areas on the outskirts of Damascus.

It also reflects attempts by the White House to avoid disputes that could hamper the widening confrontation against the Islamic State and other factions, such as the al-Qaeda-inspired Khorasan Group.

Among Assad’s backers is Iran, which is strongly opposed to the Islamic State but has so far remained outside the U.S.-led international coalition. It was not immediately clear whether Iran also was informed in advance of the airstrikes. But Russia, another ally of Assad’s government, complained Tuesday that the attacks violated international law.

The state-run Syrian Arab News Agency (SANA) said the United States informed Syria’s representative to the United Nations that it would carry out airstrikes. Psaki confirmed the contact but did not say when it occurred.

She denied, however, a SANA report that Secretary of State John F. Kerry sent a letter to Syria’s foreign minister, Walid al-Moualem, on Monday to inform him of the United States’ intention to target Islamic State positions.

Syria had previously said that it would consider strikes against Islamic State targets on its territory an act of aggression unless they were carried out in coordination with Damascus.

The U.S. Navy released video Tuesday of troops launching Tomahawk missiles against Islamic State militants. (Video courtesy U.S. Navy)

Moualem stressed that airstrikes in Syria would have limited success without collaboration with forces on the ground, SANA reported. The comments appeared to be an effort to further bolster strategic coordination with Washington despite Obama’s proposal to aid “moderate” rebels as proxy fighters against the Islamic State.

An activist in Syria, Abo Jilan, said 18 airstrikes were carried out in the north-central city of Raqqah.

“Seven of them hit the main headquarters” of the Islamic State and left it “hugely damaged,” said Jilan, who runs a group called Raqqah is Being Silently Slaughtered.

Murphy reported from Washington.