A Pakistani court has suspended a detention order on the alleged mastermind of the 2008 Mumbai attacks, government lawyers said, drawing a sharp protest from India.

India summoned Pakistan's envoy to protest after the Islamabad High Court suspended the order on the alleged mastermind of the attacks which killed 166 people.

The suspension is the latest round in a tussle over whether to grant bail to Zaki-ur-Rehman Lakhvi, who is accused over the terror siege in India's commercial capital.

The Mumbai carnage was blamed on Lashkar-e-Taiba (LeT), a banned Pakistani militant group, and India has long seethed over Islamabad's failure either to hand over or prosecute those accused of planning and organising the violence.

A court had granted Lakhvi bail on December 18 but after protests from India, the authorities ordered his detention under public order legislation.

Lakhvi's lawyers challenged the detention on Monday and the Islamabad High Court suspended the order, government lawyer Jehangir Jadoon said.

"The Islamabad High Court took Lakhvi into its custody and granted him conditional bail against surety bonds of one million rupees (USD $9,943)," Mr Jadoon said.

The suspension can be withdrawn if the government challenges it, he added.

Lakhvi remains in custody in a high-security jail, as he has throughout the 10 days of wrangling.

The paperwork involved in actually getting him released means he is unlikely to walk out of prison soon.

Nonetheless India, which has long accused Pakistani intelligence agencies of having had a hand in the Mumbai attacks, summoned the country's high commissioner.

An Indian foreign ministry official said Delhi wanted "to register our protest over the court order".

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

Seven Pakistani suspects have been charged with planning and financing the attacks but the failure to advance their trials has been a major obstacle to better cross-border ties.

The horror of the Mumbai carnage played out on live television around the world, as commandos battled the heavily-armed gunmen who arrived by sea on the evening of November 26, 2008.

It took the authorities three days to regain full control of the city and India claims there is evidence that "official agencies" in Pakistan were involved in plotting the attack.

Indian prime minister Narendra Modi said the bail order was "a shock to all those who believe in humanity world over".