Malaysia has issued a hazard warning for ships plying the Malacca Strait after thick haze caused visibility to drop along the vital waterway.

"Low visibility less then five kilometres occurring over the Straits Of Malacca and coastal waters of Sarawak due to haze is expected to continue till Thursday," the meteorological department said in a statement.

"This situation is hazardous to ships without navigational equipment," it said.

A department spokesman said visibility on Monday was at 1.3 kilometres at the western coastal city of Malacca facing the strait, and four kilometres at Senai in Johor.

"The visibility will be below five most of the time, so that's why we issued the warning there. If the situation improves, we can terminate the warning," he told AFP .

Clear conditions normally see visibility at 10 kilometres over the strait, he said.

Visibility was also poor in other parts of the country, with Kuala Lumpur International Airport at just 500 metres, although flights have not yet been disrupted.

"The airport operations are still running as normal and we are monitoring the situation," said airport spokeswoman Shuhainie Shamsudin.