ISLAMABAD: A government prosecutor said Wednesday he would file a petition next week challenging an order granting bail to the alleged mastermind of the 2008 terror attacks in Mumbai.

A judge in an anti-terror court last week granted bail to Zakiur Rehman Lakhvi, accused over the siege in India's commercial capital that left 166 people dead and was blamed on the banned militant group Lashkar-e-Taiba (LeT).

The bail decision triggered a furious response from New Delhi and Pakistani prosecutors swiftly announced they would appeal against it.

Read: Mumbai attack 'mastermind' Lakhvi detained under MPO

“We will file a petition in the Islamabad High Court next week,” prosecutor Mohammad Azhar Chaudhry told AFP.

Chaudhry had originally planned to file the appeal on Monday, but had to delay it as he had not received a written copy of the bail ruling.

Relations between nuclear-armed rivals Pakistan and India worsened dramatically after the Mumbai carnage, in which 10 gunmen attacked luxury hotels, a popular cafe, a train station and a Jewish centre.

Lakhvi remains in custody in the high-security Adiala prison in Rawalpindi after the authorities ordered his detention under public order laws following the bail decision.

Indian Prime Minister Narendra Modi told lawmakers last week that the bail order came “as a shock to all those who believe in humanity world over”.

New Delhi has long said there is evidence that “official agencies” in Pakistan were involved in plotting the attack.

Islamabad denies the charge but LeT's charitable arm Jamaat-ud-Dawa, seen as a front for the militant group, operates openly in the country.

Seven suspects have been charged with planning and financing the attacks but the failure to advance their trials has been a major obstacle to better ties between Pakistan and India.