The Thai holiday island of Phuket has been plunged into a poisonous grey haze caused by illegal forest fires in neighbouring Indonesia.

Reduced visibility caused passenger planes from Singapore and Kuala Lumpur and destined for Phuket airport to turn around on Thursday. The noxious fumes which have been spreading for weeks have shut down many other parts of south-east Asia.

Schools have been closed in Malaysia and races in Singapore for the swimming world cup – the FINA world championship – were cancelled on Saturday. A marathon in Malaysia on Sunday was also abandoned.

The Thai foreign minister on Thursday invited Indonesia’s ambassador for a meeting to discuss the forest fires, the Bangkok Post reported. Pollution rose to 200 microgrammes on Wednesday evening, classed as “very unhealthy”.

Don Pramudwinai said before his meeting with ambassador Lutfi Rauf that he wanted short and long-term solutions to a problem that is repeated annually during Indonesia’s dry season when plantation owners slash-and-burn land on Sumatra, the paper said.

Tens of thousands of people in Indonesia and Malaysia have sought medical treatment for respiratory problems. The annual burning is decades old but Indonesia has faced mounting pressure to end the practice.

Scientists warn the pollution, caused mostly from the burning of drained peatlands, could surpass 1997 levels when the smog led to an environmental disaster costing an estimated US$9bn in damage.

Greenpeace says the fires kill roughly 110,000 people a year in the region through associated conditions.

Malaysian prime minister Najib Razak said this week that Indonesia needs to convict plantation companies.

Indonesia has deployed 20,000 security forces police to water bomb the fields and use chemicals to artificially induce rainfall. It also says it has investigated companies and ordered four to suspend operations.

At first rejecting offers to help from Singapore, a foreign ministry spokesman said on Thursday that Jakarta would now work “with a number of countries including Singapore” to fight the fires.