FILE PHOTO: India's Prime Minister Narendra Modi poses after the ceremonial reception for South Africa's President Cyril Ramaphosa at the forecourt of India's Rashtrapati Bhavan Presidential Palace in New Delhi, India, January 25, 2019. REUTERS/Altaf Hussain/File Photo

MUMBAI (Reuters) - A hardline Hindu nationalist group in western India will partner with Prime Minister Narendra Modi’s Bharatiya Janata Party (BJP) in coming elections after agreeing a seat-sharing plan in Maharashtra state, the parties said on Monday.

The tie-up with the Shiv Sena, a partner in the governing coalition led by the BJP, is a boost to Modi as he seeks alliances ahead of the general election, which is due to be held by May. The Shiv Sena had said last year it would contest the election on its own.

In Maharashtra state, the Shiv Sena and the BJP would contest 23 and 25 seats respectively, state Chief Minister Devendra Fadnavis, who is also a member of the BJP, told a news conference in Mumbai, the state capital and the country’s financial capital, where the Shiv Sena is headquartered.

The Shiv Sena enjoys considerable political clout across Maharashtra. Like the BJP, it believes India is a fundamentally Hindu nation, despite the country’s secular constitution.

Maharashtra sends 48 lawmakers to parliament, second only to northern Uttar Pradesh, the most populous state, which elects 80 lawmakers.

“We have entered into the alliance to keep the opposition parties out,” Shiv Sena chief Uddhav Thackeray said.

Modi’s BJP has been scrambling to make an alliance with regional parties for the general election, which pollsters say could produce a fractured mandate.

The Samajwadi Party (SP) and the Bahujan Samaj Party (BSP), traditional political rivals in Uttar Pradesh, last month forged an alliance in an effort to defeat the BJP.

In a fillip to opposition parties, the BJP lost power in three states in December, dealing Modi his biggest defeat since he took office in 2014.