SINGAPORE - A man linked to a case involving 340,000 tonnes of stolen gas oil worth more than $200 million - the largest ever in Singapore - has been jailed for 2½ years.

The Straits Times had earlier reported that the gas oil had been stolen over several years in incidents dating back to 2014 from Shell's refinery in Pulau Bukom, the largest petrochemical production and export centre in the Asia-Pacific region.

On Thursday (July 11), a district court heard that Dang Van Hanh, 38, was the first of 15 people, including eight former Shell employees, to be dealt with in court.

His case alone involved nearly 5,600 tonnes of gas oil worth more than US$2.5 million (S$3.4 million) in total.

The Vietnamese man pleaded guilty to two counts of intentionally aiding to dishonestly receive more than 3,500 tonnes of gas oil worth about US$1.75 million.

Two other similar charges involving the remaining amounts were considered during sentencing. He committed the offences thrice in 2016 and once last year.

Dang was working as the chief officer of a vessel known as the Prime Sun when it docked at Wharf 3 at Shell at Pulau Bukom to load gas oil on Sept 9, 2016.

The captain of the vessel was another Vietnamese man, Doan Xuan Than, 47, whose case is still pending.

Deputy Public Prosecutor Christopher Ong said: "The accused was aware that Prime Sun would be receiving stolen gas oil as (Doan) had informed him when they berthed. The accused also assisted to prepare a stowage plan for gas oil on this occasion as well.

"(Doan) asked the accused to prepare for loading of the illegal gas oil at the appropriate moment. The accused would then assist to get his crew members ready for such loading. However, the crew members were unaware that Prime Sun was receiving stolen gas oil."

The court heard that nearly 2,000 tonnes of gas oil valued at around US$800,000 were unlawfully transferred that day.

According to Dang, on each occasion where he helped to receive stolen gas oil on board Prime Sun, Doan would pay him between US$1,000 and US$2,000.

Dang was the chief officer of Prime South, a Panama-registered tanker, when the vessel arrived in Singapore on Jan 4 last year. It is owned by Prime Shipping Corporation located in Ho Chi Minh City in Vietnam.

Before arriving here, the captain, who was also not named in court documents, told him that they would be receiving stolen gas oil.

On Jan 7 last year, nearly 1,600 tonnes of gas oil worth more than US$960,000 were unlawfully transferred for Shell at Pulau Bukom to Prime South.

However, police boarded the tanker later that day to arrest Dang and other individuals. He has made no restitution to Shell, the court heard.

DPP Ong said: "The offender was effectively caught red-handed after a police operation... that led to the arrest of multiple individuals across Singapore.

"Investigations have since uncovered the misappropriation of gas oil by two syndicates of Shell employees from Shell Pulau Bukom on an unprecedented scale."

On Thursday, he urged District Judge Tan Jen Tse to sentence Dang to at least 30 months' jail, stressing that these offences "have the potential to bring Singapore's reputation as a bunkering hub into disrepute".

Defence lawyer Vincent Chan pleaded for his client to receive not more than two years' jail. He told the court that Dang had played a "very minor role" in the offences.

For each count of dishonestly receiving stolen property, offenders can be jailed for up to five years and fined.