Iran's seized oil tanker Grace 1 will be freed by Tuesday evening, the country's semi-official Fars news agency quoted unidentified Gibraltar authorities as saying.

Gibraltar said on Tuesday it was seeking to de-escalate issues arising with Iran since the detention of the Grace 1 tanker by British marines in July.

‘Britain is interested in releasing Iran's oil tanker Grace 1 ... following the exchange of some documents, we hope the release will take place soon,’ the deputy head of Iran's ports and Maritime Organisation, Jalil Eslami, said in remarks reported by IRNA news agency.

British Royal Marines seized the Iranian oil tanker on July 4 off the coast of the British Mediterranean territory of Gibraltar on suspicion of violating EU sanctions by taking oil to Syria, which Iran denies.

‘The vessel was seized based on false allegations ...it has not been freed yet,’ Eslami said.

Two weeks after the capture of the Iranian tanker, Iran’s Revolutionary Guards seized a British tanker, Stena Impero, near the Strait of Hormuz, accusing it of marine violations. Britain considers that action to have been illegal retaliation.