A fugitive shipowner at the centre of a $5m US reward offer for alleged North Korea sanctions busting has been in Singapore for the last 18 months, according to local police.

Kwek Kee Seng, 62, had his passport seized by Singaporean police in April last year after he was accused by the US of delivering gasoline to North Korea in defiance of US and United Nations sanctions.

The US offer of a reward of $5m for information on Kwek last week took Singaporean police by surprise as they had been in “active communication” with the US over their investigation into the shipowner for a suspected breach of UN regulations.

“The SPF [Singapore Police Force] would like to highlight that Kwek is presently in Singapore,” it said in a statement.

Singapore’s police publicly confirmed their investigation into Kwek in April 2021 after the US said it had opened a case against him. He is accused of running an “extensive” scheme to evade sanctions that target North Korea.

The force said it told US authorities in April and May 2021 about their investigation. “Since then, there were several more exchanges,” said the force. “Due to the nature and complexity of the case, investigations are still ongoing.”

Kwek is said to have acquired the 3,912-dwt tanker Courageous (built 1987) in 2019 and used it to carry oil products to North Korea.

The Courageous — formerly known as the Sea Prima — made ship-to-ship transfers to North Korean vessels and at least one direct shipment to the west coast port city of Nampo, the US said. Kwek was said to have coordinated the transfers and supervised the vessel during the Nampo delivery.

The ship was involved in “dark” activities, including the disabling of its AIS. The crew were alleged to have made unnecessary detours to hide the origin of its cargo.

The Courageous was first detained in Cambodia in 2020. The US took custody of the ship last year and a judge agreed to its forfeiture in July.

Kwek, director of Singapore-based shipping agency and terminal operations company Swanseas Port Services Pte Ltd, is also accused of having laundered the money through the US financial system via front companies in Panama, Singapore and elsewhere.

Kwek and his Taiwanese business associate, Chen Shih Huan, and three companies linked to Kwek were put on the US sanctions list last month. Chen was said to have helped pay crew members.

Singapore’s police said it wrote to US authorities to “seek clarification” after the reward offer last week.

The US Department of State last week offered the reward for “information” on Kwek or his “illicit financial activities”. It also said that Kwek “remains at large”.

If charged and found guilty, Kwek faces up to 10 years in prison and a fine of up to $500,000 for a breach of UN regulations under the city state’s United Nations Act of 2001.