TEHRAN, July 14 (Xinhua) -- Iran's ambassador to Britain urged London to release the Iranian oil tanker that it seized last week or waits for a response from Tehran, Tasnim news agency reported on Sunday.

Hamid Baeidinejad said that Britain has breached marine regulations by its "illegal act and piracy."

The remarks by Baeidinejad come after British Royal Marines in the Strait of Gibraltar seized an Iranian ship last week which, it claimed, was heading to Syria "in breach of EU sanctions."

Iran has denied that the vessel was on its way to Syria.

"If the Iranian oil tanker is not released, the UK measure will not be left unanswered," Baeidinejad was quoted as saying.

On Friday, Iran's Foreign Ministry urged Britain to release its oil tanker "soon."

Iran's President Hassan Rouhani has also warned Britain against the "consequences" of the seizure of an Iranian oil tanker.