Former leader Mayawati called in the CBI

The Central Bureau of Investigation (CBI) accuses Prakash Chander Pandey of killing the Hindi language poet.

The case has attracted particular attention because it took place in the constituency of Prime Minister Atal Behari Vajpayee.

A former minister in Uttar Pradesh, Amar Mani Tripathi, has already been arrested in connection with the murder.

A CBI spokesman in Delhi told the BBC that Mr Pandey had been arrested on Monday morning in the state capital, Lucknow, where the murder took place.

"The man was arrested after sustained interrogation of two others who were already behind bars in connection with this case," said the spokesman.

Mr Pandey was due in court later on Monday, he said.

Murder controversy

Madhumita Shukla was seven months pregnant when she died.

Investigators said DNA from the unborn foetus matched that of the former UP state minister, Amar Mani Tripathi.

He denies any involvement in Ms Shukla's murder.

Mr Tripathi had been a minister in the Uttar Pradesh government of Chief Minister Mayawati who resigned in August after political differences with India's governing Bharatiya Janata Party.

He then switched his allegiance to the Samajwadi Party of Mulayam Singh Yadav, the new chief minister.