Voters in the Indian capital of New Delhi are going to the polls in what has become a litmus test for the popularity of Prime Minister Narendra Modi and his nationalist party.

Opinion polls ahead of Saturday's vote to choose the city's chief minister suggest that Modi's Bharatiya Janata Party is either locked in a close contest with the upstart Common Man's Party or will come in second.

The BJP has fielded Kiran Bedi, India's first high-ranking woman police officer as its candidate. She faces Arvind Kejriwal, a former income tax official turned popular anti-corruption activist.

The BJP won an overwhelming victory in national elections in May and has won several local elections since then.

India's widespread culture of graft is a key issue in this election.