Popular Thai holiday islands were engulfed with haze from Indonesian forest fires Thursday, forcing several planes packed with beach-bound tourists to turn back, further stoking regional tensions.

The travel disruptions came as Indonesia finally agreed to accept international help to douse the massive fires that have been started deliberately to clear agricultural land.

Five flights bound for the resort islands of Phuket and Samui turned back to Bangkok Thursday morning due to poor visibility, according to the Aeronautical Radio of Thailand, which controls air traffic across the country.

A further two airlines flying to Phuket from Singapore were forced to circle the airport for up to an hour before landing, it said, as haze blocked out the sun to the disappointment of visitors.

"It is the worst haze (on the island) in many years," Trakul Thotham, director of the Department of Disaster Prevention and Mitigation on Phuket, told AFP, but said it was "getting better" Thursday.

Of the seven affected southern Thai provinces Phuket has been worst-hit with unhealthy levels of particulates in the air, according to the department.

Some Thais wore protective masks to combat the pollution, Wipa Emem, a reservation clerk at the Holiday Inn Resort on the island told AFP, but tourists were mostly "still on the beach".

After weeks of insisting it could tackle the crisis alone, Indonesia Thursday said it was in talks with countries about assistance including Singapore, Russia, Malaysia, Australia and China.

"Hopefully, we can speed up our efforts," President Joko Widodo told reporters before flying to Jambi, one of the worst-affected provinces on smog-belching western Sumatra island.

But his jet was unable to land at the local airport due to the haze, presidential spokesman Ari Dwipayana told AFP, forced to divert to another airport on Sumatra.

- 'Not a handout' -

For weeks, fires illegally started to clear land for plantations on Sumatra and the Indonesian part of Borneo have shrouded Singapore and Malaysia in acrid smog, worsening air quality, closing schools and forcing the cancellation of outdoor events.

The blazes are an annual occurrence during the dry season, but scientists have warned this year's are on track to be the worst ever due to an El Nino weather system that has created tinder-dry conditions in Indonesia.

Jakarta has deployed about 25,000 personnel and aircraft, but the fire-fighters have seemed overwhelmed by the extent of the blazes.

Tensions have been rising between Indonesia and its neighbours as the haze spreads, with Singapore's biggest supermarket chain Wednesday withdrawing paper products made by an Indonesia-owned company, Asia Pulp & Paper.

Some of the group's suppliers in Indonesia have been accused over the haze.

"This remains a challenge for us so we feel it is important to cooperate with countries with resources to assist us," foreign ministry spokesman Arrmanatha Nasir told reporters in Jakarta.

He insisted it was "not a handout" as Indonesia would pay for the services with some countries as it particularly sought bigger planes for water-bombing.

The nation's disaster agency said one large Russian plane should be arriving soon to help with fire-fighting. Singapore has offered aircraft to artificially induce rain and conduct water-bombing, as well as personnel to help fight the blazes.

The city-state has been especially infuriated by the failure to tackle the fires and Indonesian officials making light of the crisis.

On Thursday there was some respite from the haze for Singaporeans and Malaysians with air quality recording moderate levels.