Firefighters in Myanmar have scrambled to put out a fire in a massive garbage dump on the edge of its largest city, Yangon, as foul-smelling smoke from the burning trash that injured dozens extended into its second week.

The fire has generated a haze blanketing parts of Myanmar's commercial hub and raised concerns about public health.

It has spread across nearly a third of the 300-acre landfill in Yangon's northern township of Hlaing Thar Yar.

Some 600 firefighters and members of security forces have been fighting the blaze since 21 April.

Authorities have imported fire suppression bio-foam from neighbouring Thailand and tried to create artificial rain to contain the spread of the flames in the peak of the hot season.

While authorities have brought the fire under control, the deputy director of the Myanmar Fire Service Department has said it was difficult to estimate when it would be extinguished.

The cause of the fire had yet to be determined.

Twenty-six people have been hospitalised, many suffering smoke inhalation.

Myanmar has sought medical help from the World Health Organisation and other aid agencies, state-run newspaper Global New Light of Myanmar reported.

Myanmar media have criticised the government's slow response in tackling what Yangon Region Chief Minister Phyo Min Thein called a "national problem".

It also highlights the growing waste problem in Yangon, a city of more than five million people without a long-term waste management solution.

The 17-year-old landfill takes about half of the city's daily trash of more than 2,500 tons.

"We have been throwing trash for ages that way. Old trash produces methane and it causes fires," Phyo Min Thein told reporters.

Firefighters described challenges battling the flames and smoke under scorching heat without adequate protective equipment.

"We can't even see each other due to the smoke," one a fire station leader who was hospitalised for smoke inhalation said.

Among the worst affected were residents of Hlaing Thar Yar, one of Yangon's poorest neighbourhoods.

Tens of thousands of people live in shanty towns there built from bamboo and plastic sheets and lack access to electricity, running water and drainage systems.

"I feel terrible because I can't breathe and my feet were swollen and still swelling a bit," said 65-year-old Tin Ohn, a Hlaing Thar Yar resident who suffers diabetes and was also hospitalised for smoke inhalation.