The embassy said in a statement that the action violated fundamental global norms.
"The illegal move by the US government to seize a Venezuelan oil tanker in the Caribbean Sea without any justified or legal reason constitutes a blatant violation of international laws and regulations, including the inviolable principle of freedom of the seas and navigation,” it said.
“‘Piracy in the Caribbean Sea' is the most appropriate title for this unlawful and unjustified move by the US, which seeks to achieve its goals by resorting to illegitimate measures, violation of national sovereignty, infringement of others’ rights, and the promotion of anarchism,” it added.
The embassy expressed Iran’s solidarity with Venezuela, saying it stood with the government and people in defending their sovereignty and rights.
Separately, US President Donald Trump on Wednesday acknowledged that American forces had taken control of an oil tanker near Venezuela, a step likely to intensify already strained relations with Caracas.
"We have just seized a tanker on the coast of Venezuela — a large tanker, very large, the largest one ever seized actually," Trump told reporters at the White House.
Meanwhile, Venezuela described the US action as an “international act of piracy.”
The Venezuelan government said, “Under these circumstances, the true reasons for the prolonged aggression against Venezuela have finally been revealed… It has always been about our natural resources, our oil, our energy, the resources that belong exclusively to the Venezuelan people.”
Washington has accused Venezuela of facilitating narcotics shipments to the United States and has increased military activity in the Caribbean, characterizing its deployment as an anti-drug trafficking mission.
The United States has conducted at least 21 strikes on alleged drug vessels in the Caribbean and Pacific since September, resulting in at least 83 deaths.
Venezuela, which holds some of the world’s largest proven oil reserves, has repeatedly said the United States is attempting to seize its resources.
In a related development, Iran’s President Masoud Pezeshkian told Venezuelan President Nicolas Maduro in a telephone conversation on Tuesday that the deployment of a US naval fleet to the Caribbean and Venezuelan waters was illegal and posed a threat to international peace and security.