By Ram Dutt Tripathi BBC reporter in Lucknow

A leader of the low-caste dominated Bahujan Samaj Party (BSP), Mayawati, has been sworn in as the chief minister of India's northern Uttar Pradesh state.

UP Assembly

SP - 145 BSP - 97 BJP - 88 Congress - 25 RLD - 14 Others - 30 Vacant - 4 Total seats - 403

She takes power for the third time by joining hands with the Hindu nationalist Bharatiya Janata Party (BJP) which mainly represents upper caste Hindus.

India's most populous state is a major political prize.

Having lost power in the February state elections, the BJP is thought to have made an indirect comeback by allying with the BSP.

No single party won an absolute majority in those polls and it took two months of horse-trading before a viable coalition could be fashioned

Opposition boycott

Immediately after the ceremony, Ms Mayawati told journalists she had joined hands with the BJP to avoid another election.

She promised full protection to the state's Muslim community, and criticised the former BJP administration for what she described as poor economic and worrying law-and-order situation.

In addition to Ms Mayawati, 19 cabinet members and four junior ministers took the oath of office in a ceremony held in the open in the state capital Lucknow on Friday.

This is Ms Mayawati's third stint in power

BSP members took 13 portfolios while the BJP got nine, and the remaining two posts went to the Indian National Lok Dal.

The newly-sworn in government will need to prove its majority in the state legislature within three weeks on the orders of the Governor.

Senior BJP leaders in Lucknow say a full cabinet with more members are expected to be appointed after the government demonstrates its majority.

The opposition Samajwadi Dal and the Congress party described the BSP-BJP coalition as an unprincipled and opportunistic alliance and boycotted the ceremony.

Uncertain prospects

Meanwhile, some Muslim leaders have appealed for a social boycott of the BSP's Muslim legislators.

They say joining hands with the BJP was against electoral promises made by Ms Mayawati.

It appears the new chief minister anticipated this reaction from the state's sizeable Muslim community and is already looking ahead to the future.

She has promised to contest the next national legislative elections in Uttar Pradesh in alliance with the BJP.

Despite this long-term commitment, given their fundamental differences, observers are sceptical about the success of this third attempt at power-sharing between the BJP and the BSP.

The first sign of unease came from former Chief Minister Raj Nath Singh, who told the BBC soon after Friday's ceremony he wanted to step down as leader of the BJP's UP legislative party.

It is understood that Mr Singh does not support the BSP-BJP coalition.