PATNA: Ten more children died Tuesday from a mysterious brain fever potentially linked to lychees, officials said, taking the death toll to 113 this month and sparking angry protests in India's poorest Bihar state.

Sixty children, mostly under the age of 10 and malnourished, are undergoing treatment after an outbreak of Acute Encephalitis Syndrome (AES) in Muzaffarpur district of the eastern state.

Bihar health department official Ashok Kumar Singh told AFP that ten children died on Tuesday, taking the overall death count in June to 113.

"Six children were discharged after being treated for AES," Singh said.

He warned that the toll may rise with fresh cases trickling-in, as dozens undergo treatment in packed hospital wards. Television images showed several children to a bed.

On Tuesday, dozens of people gathered outside the main hospital in Muzaffarpur to accuse local authorities of acting too slowly and of not caring.

The state's health minister came in for particular criticism after asking reporters about the score in India's cricket match against Pakistan on Sunday during a news conference on the crisis.

"Bihar's Health Minister Mangal Pandey seems more worried about cricket score than the death of children," tweeted Randeep Surjewala of the opposition Congress party.

Rabri Devi, another opposition figure, called the deaths "cold-blooded murder".

"Children are dying because of a lack of medicines and treatment," she tweeted.

Bihar Chief Minister Nitish Kumar Tuesday faced angry protesters as he made his first visit to the state-run Sri Krishna Medical College, where most of the children have died.

Reporters were barred from entering the facility, and the families of sick children were kept away from the premises.

- Outbreaks occur annually -

The disease sets in rapidly and is characterised by plummeting blood sugar, high fever, convulsions and paralysis. It is caused by viruses, bacteria and toxins spread in different ways.

Outbreaks have occurred annually during summer months in the same districts since 1995, typically coinciding with the lychee season.

Apart from 2014 when a record 357 children died in the state, the annual death toll is usually much lower.

Several years ago US researchers said the brain disease could be linked to a toxic substance found in lychees, the tropical fruit.

They also said more study was needed to uncover the cause of the illness, known locally as Chamki Bukhar, which is fatal in a third of cases.

The National Human Rights Commission has asked Prime Minister Narendra Modi's government and Kumar state authorities to report any "possible flaw" in implementation of vaccination and awareness programmes.

An editorial in the Hindu newspaper Tuesday said the deaths could have "easily been prevented with some foresight and early care".

It said in 2014 an Indo-US expert team had saved 74 percent of sick children through a simple medical intervention.

"It is appalling that this year the government failed to raise awareness on this strategy."

Bihar is one of India's poorest states and home to almost 100 million people. It has also been hit by a heatwave in recent weeks with temperatures of 45 degrees Celsius (113 Fahrenheit) that has left 91 people dead since the weekend.

Most of the children affected by the brain fever come from poor families who struggle to get even one healthy meal a day. Often the kids gorge on free-growing lychees on an empty stomach. —AFP