Twenty-two men have been jailed after they illegally transferred more than 200 tonnes of marine fuel oil worth over $112,000 from one vessel to another in separate incidents.

They were each jailed for between two and seven months on Wednesday.

Two of them are Singaporeans - Teo Chai Heng, 39, and Lim Kim Hock, 40 - who worked for a locally registered company, Brightoil Petroleum (Singapore). They were bunker clerks of Brightoil 326 - a Singapore-registered tanker.

The pair were jailed for five months after pleading guilty to one count each of engaging in a conspiracy with 11 of their Indonesian colleagues to commit criminal breach of trust by dishonestly misappropriating 35 tonnes of marine fuel oil worth $17,891.

The Indonesians include the captain of Brightoil 326, Robby Lirpa Sugiharto, 34, who had the stiffest sentence of seven months' jail.

The other nine men dealt with in court on Wednesday are also Indonesians, but they worked on a Tanzania-registered tanker vessel called Common 1.

They include its captain, Stenlly Kart Baule, 38, who was jailed for five months, and chief officer Franner Virty Einstein Sabaru, 28, who was jailed for four months.

Eight of them pleaded guilty to two counts each of engaging in a conspiracy to dishonestly receive stolen property.

The ninth man, Herslag, 45, who goes by only one name, admitted to a single charge and was jailed for two months.

The court heard that Brightoil 326 loaded some marine fuel oil in Singapore at around 5pm on Feb 4, and Teo found out the vessel was carrying an excess of about 35 tonnes of the fuel.

He informed Lim, who then contacted a man known only as Raf to arrange for a foreign vessel to collect this excess amount.

At around 2am the next day, another man, known only as Hardiyanto, told Stenlly to sail to the sea off Bedok to collect the marine fuel oil.

Common 1 pulled up beside Brightoil 326 about an hour later and the fuel was transferred through a hose.

Separately, the court heard that Stenlly and seven members of his crew committed a similar offence when they entered Singapore on Jan 19 on the same vessel. It was then known as Elfa 18 and was Lesotho-registered.

At that time, Malaysian Akrim Mohamad Nor, 25, was a bunker clerk for locally registered company Fratelli Cosulich Bunkers Singapore and was working on board a tanker known as Kai Ei Maru 8.

Deputy Public Prosecutor Jordon Li said Akrim had contacted Hardiyanto to arrange for the Singapore-registered Kai Ei Maru 8 to illegally transfer marine fuel oil to Elfa 18.

Hardiyanto alerted Stenlly, who steered his vessel to the sea off Tanah Merah at around 8pm on Jan 19. Through a hose, 189 tonnes of marine fuel oil worth $94,705 was transferred from Kai Ei Maru 8 to Elfa 18. The case involving Akrim is still pending.