Indonesian maritime authorities seized an Iranian-flagged tanker carrying more than 200,000 metric tons of light crude oil after a suspected illegal transfer at sea, they said Tuesday.

Iran has been accused by the United States and its allies of using crowded shipping lanes in the Persian Gulf and elsewhere to circumnavigate Western sanctions on its nuclear programme.

The MT Arman 114 under the Iranian flag was “suspected of carrying out illegal transshipment activities” in Indonesia’s exclusive economic zone, the maritime security agency said in a statement.

The tanker was seized on Friday after authorities found it conducting a suspected transfer of crude oil to Cameroon-flagged ship MT S Tinos, the statement said.

“The two ships were caught red-handed carrying out crude oil transshipment activities,” it added.

The vessel was carrying a crew of 28 Syrian nationals and three other passengers, as well as 272,568 metric tons of light crude oil worth tens of millions of dollars.

The agency did not directly link the transfer to the Iranian government or accuse Tehran of involvement.

In May, the two countries signed a trade agreement in Indonesia’s capital Jakarta, where President Joko Widodo hosted his Iranian counterpart Ebrahim Raisi, as Tehran looked to boost its international trade ties.

Indonesia’s maritime authorities said the tanker refused to respond to communication from Indonesian authorities, had turned off its shipping information system, and did not fly its flag.

The listed owner of the vessel did not respond to a request for comment.

When approached, the MT Arman 114 tried to escape before being chased into Malaysia’s exclusive economic zone.

Indonesian authorities carried out the seizure with the help of Malaysian authorities, who “deployed special maritime troops using helicopters”, it said.

Tehran has increased actions against tankers in the Persian Gulf since the United States tightened sanctions on Iran’s oil exports and other areas of its economy.

The US military said last week it had blocked two attempts by the Iranian navy to seize commercial tankers in international waters off Oman, including one case in which the Iranians fired on the tanker.

The tightened US sanctions, which aim to cut into Iran’s export earnings, have led to the United States seizing Iranian-controlled tankers and shipments of crude to other countries.

President Joe Biden took office hoping to return to a 2015 nuclear accord with Iran that had been scrapped by his predecessor Donald Trump.

But EU-mediated talks collapsed and mass protests in Iran made Washington increasingly hesitant to strike a deal with the clerical state.

By Agence France-Presse