Two government workers having an affair were caught throwing a sickie and romping in a car.

The pair - who are colleagues - aroused suspicions when the white Toyota was seen rocking suspiciously next to Trikora Beach, on Riau Islands, Indonesia on November 3.

Locals through the car had broken down and went to help. But they were shocked when they saw the half-naked man and woman having sex.

They were both wearing the top halves of their brown council uniforms and the woman's orange jacket was slung across the front seat.

After being disturbed, the man immediately whipped his underpants back on and sped away as furious locals gave chase.

Mo Mohammad, one of the angry mob, said: "We thought perhaps they needed help because their car was broken down and that they had parked it there for repair, but we were surprised that they were doing something else.

"We would have let them be, but they are wearing government uniforms and doing it during working hours so we tried to take their identities."

The woman was seen blocking the windows from the residents who started filming while her partner was busy putting his trousers back on so he could drive.

The Regional Secretary of the Bintan Regency Government, Adi Prihantara, received complaints about the incident and confirmed that the pair were colleagues from the secretariat department of his agency. They are both married to different people.

The official said the pair did not report for work that day and called in sick, but he refused to reveal their identities. He has now started an investigation.

Adi said: "We will summon them to our office to explain what happened. I am truly disappointed with their actions."

The couple are expected to receive sanctions for "misconduct" and "tarnishing the good name of the civil service office."