The Indian Prime Minister Narendra Modi has admitted defeat for his governing BJP in a key regional election in Bihar state.

The BJP was running against an alliance of parties linked to main opposition Congress party in the state assembly.

Mr Modi won a convincing victory in last year's national elections, but this poll was seen as a referendum on his economic programme.

Defeat is a major setback, says the BBC's Sanjoy Majumder in Delhi.

However, a spokesman for the Hindu-led nationalist party rejected suggestions the result for the state assembly was a personal blow for Mr Modi, saying the BJP "managed a creditable performance".

The prime minister had been hoping a victory in Bihar would boost his party's strength in India's upper house of parliament, which made up of representatives of state legislatures and where he lacks a majority.

With votes still being counted, the anti-Modi alliance was ahead in 125 seats, compared with the BJP's 79 seats, out of 238 where the trends were clear.

Bihar, in the north-west of the country, is one of India's largest states, with a population of 100 million, and is also one of the poorest.