US launches retaliatory airstrikes following deadly attack on American base in Syria

WASHINGTON -- The conflict in Syria is escalating after new attacks on U.S. bases, following drone strikes in Syria that killed an American and left others injured. The U.S. launched its own airstrikes in retaliation.

Overnight Friday, two new attacks targeted U.S. bases in eastern Syria.

U.S. officials told ABC News that five rockets were fired at one facility, injuring a U.S. service member. In the other attack, drones targeted the facility, but two out of three were shot down.

These latest incidents make four attacks on U.S. forces in Syria in just 36 hours, with at least one of them being deadly.

The U.S. hit back, using F-15's to destroy two Iranian-backed training and equipment facilities in Syria.

"Make no mistake, the United States does not seek conflict with Iran but be prepared for us to act forcefully to protect our people. That's exactly what happened last night," President Biden said.

Iran has condemned the retaliation, calling the targets "civilian points" and saying it led to the death of seven martyrs.

On Thursday, an Iranian drone carrying explosives detonated at a U.S. base in northeastern Syria, killing an American contractor. It is the first time an American has been killed in Syria by a drone strike. It also injured another contractor, as well as five U.S. service members.

These incidents have almost become commonplace after nearly 80 rocket or drone attacks by Iranian-backed proxies the last two years.

As of Saturday, there are 900 U.S. service members and many more contractors in Syria to defeat ISIS.

When President Biden was pressed on these attacks, he said, "We're not going to stop."

Biden officially notifies Congress of Syria airstrike

President Joe Biden on Saturday notified Congress of his decision to authorize an airstrike in Syria this week against what the US said were Iranian-affiliated facilities.

The US airstrike came after a suspected Iranian drone struck a facility housing US personnel in the country, killing an American contractor and wounding five US service members.

The strikes, Biden said in his letter to Congress, were made, "in order to protect and defend the safety of our personnel, to degrade and disrupt the ongoing series of attacks against the United States and our partners, and to deter the Islamic Republic of Iran and Iran backed militia groups from conducting or supporting further attacks on United States personnel and facilities."

The president added that the US strikes "were conducted in a manner intended to establish deterrence, limit the risk of escalation, and avoid civilian casualties."

Saturday's notification is a routine part of the War Powers Act, which requires the president to notify Congress within 48 hours of military actions. The letter was sent to both House Speaker Kevin McCarthy and President Pro Tempore of the Senate, Sen. Patty Murray.

The strikes are likely to increase tensions with Iran, with which the proxy groups are aligned, though Tehran isn't always involved in directing attacks that they conduct.

The US has already sanctioned Tehran for providing attack drones to Russia to use in the war in Ukraine. And on Thursday, Chairman of the Joint Chiefs of Staff Gen. Mark Milley reiterated US concerns that Iran has the potential to produce enough fissile material for a nuclear weapon in less than two weeks and manufacture one within months.

Brig. Gen. Patrick Ryder, the Pentagon spokesman, emphasized to reporters Friday that the US is not seeking conflict with Iran, but said the strikes "were intended to send a very clear message that we will take the protection of our personnel seriously and that we will respond quickly and decisively if they're threatened."

CNN contributed to this post.