Iran on Friday condemned the US military strike in eastern Syria bordering Iraq, terming it "illegal aggression".
Foreign Ministry spokesman Saeed Khatibzadeh, in a statement, said the attack constituted a "violation of human rights and international law".
The strike, ordered by President Joe Biden, was carried out in the wee hours of Friday morning and targeted Iran-backed militias in Syria-Iraq border region.
The Pentagon said the airstrike destroyed "multiple facilities" belonging to militia outfits and was in retaliation to recent attacks against US and coalition forces in Iraq, including in Erbil.
There are conflicting reports about casualties in Friday's military strike, with militia groups confirming one dead and around two dozen injured.
Khatibzadeh, in his remarks, said the US airstrike was a "continuation of the Zionist regime's aggression on Syrian soil," referring to Israeli airstrikes in the war-ravaged country.
"The US forces have illegally entered Syrian territory in recent years, occupying areas of its territory and stealing natural resources, including oil," the spokesperson added.
He described the military action as "clear violation of Syria's sovereignty and territorial integrity," warning that it could "exacerbate military conflict and further destabilize the region."
Earlier in the day, Foreign Minister Javad Zarif in a telephonic talk with his Syrian counterpart Faisal Mekdad also stressed the need for "Western powers’ compliance with the UN Security Council resolutions on Syria and the need for respecting sovereignty and territorial integrity of the Arab country."
The attack is likely to derail recent efforts to de-escalate tensions between Tehran and Washington, according to observers.