MILLIONS are choking on toxic air and struggling to breathe in the world’s most polluted city, with the streets enveloped in thick smog.

Vietnam’s capital, Hanoi, is being suffocated by hazardous, cancer-causing air particles sparked by miles of burning rubbish and heavy traffic.

The city’s air is so dire that it has been ranked as the world’s most polluted city, with six times higher pollution levels than London.

Conditions are so bad that Hanoi’s nine million residents are warned to wear masks and limit their time outdoors.

Health officials say that those who frequently breathe the world’s worst-quality air are at risk of strokes, asthma, heart disease and lung cancer.

Resident Nguyen Ninh Huong, 21, said she initially mistook the thick smog enveloping the city’s skyscrapers for fog.

She said: “At first I thought it was foggy … but later I found out that it is actually fine dusts that reduce my vision and make me feel like it is not healthy to breathe.”

The nation, one of Asia’s fastest-growing economies, has battled severe air pollution challenges for many years.

However, residents feel the poor air quality has recently become even more toxic.

Resident Luu Minh Duc, 64, said: “We, the elderly, can feel it very clearly when we suffer from respiratory problems that lead to breathing difficulties,” she said

The densely-populated capitals pollution levels are over 50 times higher than recommended guidelines.

Hazardous small particles known as PM2.5 reached a staggering 266 micrograms per cubic meter (μg/m³) in Hanoi on early Friday, according to AirVisual, which provides daily independent global air pollution information through a mobile app.

PM2.5 are cancer-causing microparticles small enough to be absorbed into the bloodstream through the lungs.

Other severe air pollutants include nitrogen dioxide (NO2), which can cause chest pain, bronchitis and asthma.

During a meeting with the transport ministry on Thursday, Deputy Prime Minister Tran Hong Ha emphasised the urgent need to transition to electric vehicles.

Tien Phong newspaper reported Ha stating: “This is the responsibility of the state to the people, and there must be specific and timely actions,”

City authorities aim for at least 50% of buses and 100% of taxis to be electric vehicles by 2030.

Following Hanoi on the list of the most polluted cities are Delhi in India, Sarajevo in Bosnia and Herzegovina, and Dhaka in Bangladesh.

Europe’s most polluted city is Skopje, the capital of North Macedonia.