At least 30 Indian migrant workers were killed on Saturday in road accidents as they tried to return to their home villages during a nationwide coronavirus lockdown, officials said.

The accidents, in central and northern India, were the latest involving some of the millions of labourers left stranded and jobless by the seven-week shutdown.

Scores have died in road and rail accidents and even from exhaustion walking home.

In the most deadly incident, a truck carrying about 40 labourers struck another vehicle also carrying workers and their families that was parked at a roadside cafe in Uttar Pradesh, local magistrate Abishek Singh told AFP.

It is thought the driver of the truck had fallen asleep, Singh said.

"The vehicle was carrying lime powder which suffocated many of those who died, all of whom were men," he added.

Indian Prime Minister Narendra Modi called the accident "extremely tragic" in a Twitter post and said relief work was in "full swing" at the scene.

A drunk driver was blamed for the second accident, in Madhya Pradesh, when a truck bringing labourers back from neighbouring Maharashtra state overturned, local official Shashi Mishra said.

Four of the five dead were women and 17 people were injured, he added.

The millions of labourers, who live off subsistence wages, have become a major concern for the government as it prepares to ease the lockdown from Monday in a bid to get the economy moving again.

More cases than China

The Indian government has responded to criticism of its handling of the migrant-labourer crisis by promising extra finance to get those stranded back home and provide food rations.

Many businesses shut down overnight after the lockdown began on March 25, leaving millions suddenly out of work.

Desperate to return to their home states, many migrants have walked hundreds of kilometres or hitched rides on trucks.

Sixteen were killed this month when a train ran over them as they slept on a railway track.

The government is also battling a surge in coronavirus cases in major cities like Mumbai and New Delhi as it prepares to ease the lockdown.

Cases in India rose by nearly 4,000 overnight to 85,940, eclipsing the number officially registered in China — where the pandemic started last year. India's death toll is 2,752, while China's stands at 4,633.

Economist Shamika Ravi, who advises the government and is a much-watched commentator on coronavirus in India has warned that the country must do more to control the outbreak in Mumbai, Delhi and other cities.

With the pandemic still weeks away from peaking, Mumbai has already run out of hospital beds to treat coronavirus patients.

Health Minister Harsh Vardhan recently told AFP that India had reacted faster to the pandemic than many richer countries and controlled it better.