Ho Chi Minh City and several localities in southern Vietnam have been enveloped in fog over the last couple of days, and the phenomenon may stem from as far away as Indonesia, a meteorology expert said on Tuesday.

As of late Tuesday afternoon, the haze was still visible in District 1, District 2, District 4 and District 9 in Ho Chi Minh City, while fishermen sailing off Ba Ria-Vung Tau Province said it was so foggy that ships could not see each other within a distance of two nautical miles (3.7km).

Since earlier this week, the waters off the south-central province of Khanh Hoa and Kien Giang Province in the Mekong Delta have been wrapped in what fishermen described as “a milky layer of air,” they told Tuoi Tre (Youth) newspaper on Tuesday.

“Such descriptions suggest that the phenomenon is likely to be dry haze,” Le Thi Xuan Lan, a weather pundit based in Ho Chi Minh City, told Tuoi Tre.

Dry haze is a phenomenon when there are fine dust particles in the air, which reduce horizontal visibility and give the atmosphere a characteristic hazy appearance.

Such particles are too small to be individually apparent, but are visible in large numbers.

The phenomenon is partly affected by the haze crisis caused by the forest fires in Indonesia, according to the meteorology expert.

“The burning of forests [in Indonesia] has blanketed many Southeast Asian countries in haze, especially areas of low latitude that sit close to Indonesia such as southern localities in Vietnam.”

Indonesia has come under growing pressure from its neighbors in recent weeks as thick smoke from fires on Sumatra and the Indonesian part of Borneo has sent pollution levels soaring in many regional nations, according to AFP.

Malaysia and Singapore have closed schools and canceled major outdoor events due to the choking haze.

These types of blazes flare up annually during the dry season as fires are illegally started to clear land for cultivation.

Adding to the problem, an El Nino weather system has made conditions drier, with this year's haze on track to be the worst on record, AFP said in a report on Tuesday.

Lan added history shows that neighbouring countries have always been affected by forest fires in Indonesia, especially when the El Nino weather effect occurred.

The same phenomenon happened during the severe El Nino periods during 1997-1998, 2002-2003, 2006-2007, and 2009-2010, according to the expert.

The current El Nino is expected to peak around the end of the year and will then rapidly weaken within three months, Lan said.

“The forest fires will continue in the future and Vietnam may be enveloped in dry haze or fog again, too,” she concluded.

Below are photos of Ho Chi Minh City on hazy Tuesday:

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