If the United States targets its bases after attacking Syria, Iran threatens a “immediate counter-reaction.”

Tehran has issued the threat after a drone attack that left an American contractor dead sparked a series of tit-for-tat strikes in Syria.

Strikes on Iranian-linked bases will be met with an “immediate counter-response” after the reported deaths of 19 people in US attacks on Syria, an Iranian security spokesperson has warned.

Keyvan Khosravi made the remarks after the US carried out a series of strikes on the east of the country in one of the deadliest exchanges between American and Iranian-aligned forces in years.

The US strikes were in response to a drone attack on Thursday that left one American contractor dead and another wounded along with five US troops.

Washington said the attack was from Iran.

In a string of tit-for-tat strikes that followed, officials said another US service member was wounded and local sources said suspected US rocket fire hit more locations in eastern Syria.

US air raids on pro-Iran installations killed three Syrian troops, 11 Syrian fighters in pro-government militias and five non-Syrian fighters who were aligned with the government, according to the UK-based Syrian Observatory for Human Rights.

The monitor’s head Rami Abdel Rahman could not specify the nationalities of the foreigners.

Iran has said its forces and allied fighters are in Syria at the request of Damascus and sees US forces as occupiers.

Mr Khosravi, spokesperson for Iran’s top security body, was quoted by the semi-official news agency Nournews as saying: “Any pretext to attack bases created at the request of the Syrian government to deal with terrorism and Islamic State elements in this country will be met with an immediate counter-response.”

It comes after President Joe Biden on Friday warned Iran the United States would “act forcefully” to protect its people.

Iran has been a major backer of President Bashar al-Assad during Syria’s 12-year conflict.

Iran’s proxy militias, including Lebanese group Hezbollah and pro-Tehran Iraqi groups, hold sway in swathes of eastern,
southern and northern Syria and in suburbs around the capital.

Tehran’s growing entrenchment in Syria has drawn regular Israeli air strikes but American aerial raids are more rare.

The US has been raising the alarm about Iran’s drone program.