However, Kedah police say no report has been lodged in relation to the allegation.
The Chinese article was posted on backpackers.com.tw on Sept 10 by an user with the pseudonym 'dr995'.
According to the posting, the author was driving a rented MPV in Langkawi, heading to the guesthouse he was staying at when the vehicle was stopped at a police roadblock.
"I rolled down the window and handed over my international driving licence to the police. He looked into the car and instructed me to park my car by the side of the road...
"He then said the car was overloaded and each of us (in the car) had to pay a fine of RM300 or else he would take us to the police station. We can only leave after paying the fine.
"Then he confiscated my passport. We appealed to the police but after a round of negotiations, he maintained his stand and wanted us to prepare the money fast. Then he continued to inspect other vehicles," the article says.
The author claimed that two policemen later intimidated him with "unbelievable remarks" and offered a deal to solve the problem - to offer them RM500.
"Not only we can leave and continue to drive our car, he also guaranteed that there will be no police causing us trouble any more."
Describing the cops as "a bunch of gangsters in police uniform equipped with pistols", the author said all the vehicles stopped by them were driven by tourists, whereas those driven by locals were allowed to pass the roadblock without inspection.
The policeman then took the author to the back of a police car so that they would not be seen by other road users and directed him to put the money into his hand.
"He then immediately covered it with a piece of paper and kept it in the police car. The process was swift and smooth, which must be the result of repeated practice.
"Aftter paying the money, I got back my licence and passport, and left the scene helplessly," he wrote.
The whole conversation with the police, he said, was secretly recorded by a fellow passenger, using a mobile phone and photographs of the policemen were also taken.
The evidence has been submitted to Taipei Economic and Cultural Office in Malaysia, he added.
One photograph showing three uniformed policemen inspecting vehicles at the roadblock was posted together with the article on the online forum.
In another posting, the author further explained that there were eight passengers on the SUV he had rented and the car rental company had assured him that he did not breach any traffic rule.
However, after the car rental company complained about the bribe incident to the police, the police changed their tune and claimed that the rear passengers were not buckled-up.
"Indeed our rear passengers were not buckled up, so we could not argue since we had breached the law... but why didn't the police use this reason then to fine us? I really don't know.
"God knows even if we had buckled up, would there be other reasons (to penalise us)? God knows even if I paid the fine without giving 'protection fee', would there be other traffic rules (to penalise us)?
"They should have killed me with a stab, no need to intimidate me for money," he wrote.
Also reporting on the matter, Sin Chew Daily today quoted Kedah police chief Ahmad Ibrahim as saying the police could not take action on the matter because it was only an online posting, with no official police report made.
Ahmad said the police would hand the case to the Malaysian Anti-Corruption Commission (MACC) if a report was lodged by the tourists.
Since the complaint was just made on an online forum, police would ignore it, he added.
Langkawi district police chief Harrith Kam also confirmed that no report on the matter has been lodged to date.
Harrith explained that foreign tourists would have to clear their traffic fines on-the-spot as this was to prevent them from leaving the country with outstanding fines.