India's ruling party led by Prime Minister Narendra Modi has suffered a serious defeat to a regional party in a key state election.

The legislative election was held on Saturday in the capital New Delhi. The results were announced on Tuesday.

The election commission said of the 70 seats up for grabs, 62 were won by Aam Aadmi Party, or common man's party. Modi's Bharatiya Janata Party secured only eight seats, adding five more seats from the previous election in 2015.

The setback came despite Modi and other leading BJP members running a vigorous campaign ahead of the poll.

The BJP enjoyed a landslide victory in the general election last May. But it has suffered a string of state elections since then.

The country's economy has begun slowing down. And criticism of Modi's government has also expanded across the nation, with critics accusing the Hindu nationalist party of carrying out discriminatory policies against minority Muslims.

Local media say these factors may have contributed to the defeat.

NHK