An oil tanker left a 20-litre oil slick near Pattaya Beach in Thailand.

The Singaporean-flagged Phoenix Jamnagar vessel was battered by severe weather during an oil transfer at the Single Buoy Mooring 2 terminal off Sriracha, on June 5.

More than 20,000 litres of fuel leaked into the sea, prompting authorities to immediately halt the oil transfer.

Thai Oil which operates the Sriracha terminal reported the leak to the Thailand Maritime Enforcement Coordinating Center at 6:05 am today, June 6.

Patches of black and brown pollutant were scattered in a 10 by 10 metre area off the coast. Booms and chemical dispersants were used to contain the spill and limit its spread.

In a statement, Thai Oil said: 'Thai Oil Public Company Limited would like to inform the public that on June 5 at approximately 11:54 pm, there was a crude oil leakage at Mooring Buoy No. 2 (SBM-2) of the Thai Oil Refinery in Sriracha, Chonburi, due to high waves and strong winds.

'The company has stopped the oil transfer in accordance with standard safety procedures. After that, the Breakaway Coupling mechanism worked as designed to prevent structural damage. However, during the valve shutdown phase, some oil leaked out. This system was designed to prevent damage to SBM-2.'

Thai Oil said containment booms had been pre-deployed before the transfer. It added there was no further leakage and no injuries were reported.

Preeyaporn Suwanaged, director-general of the Pollution Control Department, said they were continuing to monitor the spill's environmental impact and were providing technical assistance.