MANAUS, Brazil, Oct 14, 2023 (BSS/AFP) - Manaus, the largest city in Brazil's Amazonas state, has for days been engulfed by a toxic cloud of smoke from forest fires lit by what the government labeled "criminals".

The city of nearly two million people has been forced to cancel some public events including a marathon.

The fires in the Amazon have produced a blanket of grey smoke over the capital of the northern state of Amazonas since Wednesday.

Air quality in the city is among the worst in the world, according to the World Air Quality Index.

"This smoke is hurting us. People don't know what they are doing by burning the forest, and many animals are dying," said Maria Luiza Reis, a 72-year-old Manaus resident.

"It's sad, and it causes us difficulties. I wear a mask so I don't breathe that toxic air because I already have health problems," she added.

Health authorities have urged city inhabitants avoid exposure as much as possible.

There are "significant risks, mainly respiratory diseases" for those exposed to smoke, said Marcio Garcia, a director with the government's public health emergencies department.

Amazonas, Brazil's biggest state, has suffered the worst October in terms of fires in the last 25 years, according to data from the National Institute for Space Research (INPE).

INPE has registered 2,770 fire outbreaks so far this month as of Thursday, a 154 percent increase compared to the same period in 2022.

The government announced on Friday it was deploying two helicopters and an additional 149 firefighters to supplement an almost equal number already fighting the fires in the region.

Environment Minister Marina Silva blamed the fires on "criminals" who light them to clear the forest for farming.

"There is no natural fire in the Amazon," Silva told a news conference on Friday.

The fires come as the region is experiencing an exceptionally severe drought, aggravated by the El Nino weather phenomenon, which has caused the level of some rivers to drop drastically.

"It is an extremely serious situation," said the minister.

Cancellation of the marathon left some runners disappointed.

"I came from Goiania specifically to run the marathon on Sunday, but it was canceled. It's frustrating," said Zacharias Martins.