An Indian man has been arrested after upsetting his football-mad neighbours by tearing up a Portugal flag, hoisted for the World Cup, when he mistook it for the emblem of a controversial Islamist group.

Social media footage showed Deepak Elangode pulling the flag off its hoisting and violently tearing it into strips before casting the fragments onto the roadside in the small town of Panoor in southern Kerala state.

The flag had been put up by local fans of star player Cristiano Ronaldo and his Portuguese team. They then rushed to confront and rebuke the vandal, local media outlet Mathrubhumi reported.

A police officer in Panoor confirmed to AFP that Elangode was arrested for causing a public nuisance but later released on bail.

Portugal's red-and-green flag bears a resemblance to that of the Social Democratic Party of India (SDPI), and local reports said the man was expressing his disdain for the group.

The SDPI is the political wing of the Popular Front of India, an Islamist movement that was banned in September for alleged terrorism links but still has a solid base of support in communities around Panoor.

Kerala is a bastion of football fanaticism in a country better known for its obsession with cricket.

Every four years, towns around the state throw up a kaleidoscope of blue, gold and green to show their support for rival football powerhouses Brazil and Argentina as the World Cup looms.

Ronaldo's star power has broadened Portugal's Indian fan base outside of its traditional bastion further north in Goa, a popular resort destination that was for centuries colonised by the Portuguese.