WASHINGTON, March 23 (Aljazeera) - The United States military has said it carried out multiple air strikes in eastern Syria against Iran-aligned groups who it blamed for a deadly drone attack earlier that killed a contractor, injured another, and wounded five US troops, the Pentagon said.

The US attacks late on Thursday night were in retaliation for an attack against a US-led coalition base near Hassakeh in northeast Syria at approximately 01:38pm (10:38 GMT) the same day, the Pentagon said in a statement.

US intelligence has assessed that the drone was Iranian in origin and US Defence Secretary Lloyd Austin said the strikes targeted groups affiliated with Iran’s Islamic Revolutionary Guards Corps in eastern Syria.

“The airstrikes were conducted in response to today’s attack as well as a series of recent attacks against Coalition forces in Syria by groups affiliated with the IRGC,” Austin said in a statement.

Austin said he authorised the retaliatory strikes at the direction of US President Joe Biden.

“As President Biden has made clear, we will take all necessary measures to defend our people and will always respond at a time and place of our choosing,” Austin said.

“No group will strike our troops with impunity.”

US forces entered Syria in 2015, backing allied forces in their fight against the IS group, also known as ISIL.

The US maintains the base which was attacked near Hassakeh and there are an estimated 900 US troops deployed in the country – and even more contractors – including in the north of Syria as well as in the south and east.

Overnight, videos on social media purported to show explosions in Syria’s Deir Ez-Zor, a strategic province that borders Iraq and contains oil fields, the Associated Press reported.

Iran-backed militia groups and Syrian forces control the area, which also has seen suspected air attacks by Israel in recent months allegedly targeting Iranian supply routes.

Syria’s state-run SANA news agency did not immediately acknowledge any US strikes.

Syria’s mission to the United Nations did not immediately respond to a request for comment.

There was no immediate reaction from Iran over the strikes.

Two of the injured US troops were treated at the base in Syria while three other wounded US soldiers and the US contractor were evacuated to a coalition medical facility in Iraq, the US Department of Defense said.