Chilean authorities are suing the giant breakfast cereal-makers Nestle and Kelloggs for putting children's cartoon characters on packets of fattening food in breach of an anti-obesity law, officials have said.

The government's National Consumer Service said in a statement it had filed a suit against the two companies plus Masterfoods, distributor of M&M chocolates, under June's "Food Labelling Law."

It accuses the companies of breaching the law by "using children's characters on packets of various products classed as 'high in'" certain unhealthy ingredients.

It said the companies had argued they had a commercial right to use the illustrated children's characters as a brand symbol.

Chile passed the law on 27 June aiming to curb high levels of obesity.

Chilean authorities estimate that one in three children under six in the South American country suffers from excessive weight.

The law obliges manufacturers to add warnings to packets of food high in sugar, saturated fats and other fattening nutrients.

It banned manufacturers from putting children's cartoon characters on products such as boxes of sugary breakfast cereals.

It also outlawed the selling of snacks that include toys, such as "Kinder Surprise" chocolate eggs and McDonalds "Happy Meals."

SERNAC director Enrnesto Munoz said the body was demanding a $110,000 fine for each company.