A gas leak at a chemical factory owned by a South Korean company in southern India has left at least 11 people dead and about 1000 struggling to breathe.

The chemical styrene, used to make plastic and rubber, leaked from the LG Polymers plant in the city of Vishakhapatnam in Andhra Pradesh state while workers were preparing to restart the factory after a coronavirus lockdown was eased, officials said.

Videos and photos from the area showed dozens of people, including women and children, lying unconscious in the streets, arms open wide with white froth trailing from their mouths.

Hundreds of people fled from Thursday’s gas leak, some on motorbikes and others carried in open trucks. Some who couldn’t find vehicles raced away barefooted, many with small children slung across their shoulders.

An injured man is carried to an ambulance. Photo: Getty

Police officers, some wearing gas masks, rushed from house to house and evacuated about 3000 people. Struggling to breathe, many people lay on the road as passers-by helped them with water.

The leak was suspected to have come from large tanks left unattended because of the strict coronavirus lockdown in the past six weeks.

The lockdown was eased on Monday, allowing neighbourhood shops and factories to resume activities.

The deadly gas leaked from two 5000-tonne tanks. Photo: Getty

Officials said a blanket of gas spread over a radius of about three kilometres, sickening people in at least four villages.

Rescuers broke open the doors of village homes that were locked from the inside and found some people who had collapsed. They were taken to hospitals.

A neurotoxin, styrene gas can immobilise a person within minutes of inhalation and be deadly at high concentrations.

-AAP