QUETTA, Pakistan: Pakistani Shiites on Saturday demanded that the head of a banned Sunni militant group be put on trial, a day after he was arrested following deadly sectarian attacks in the city of Quetta.

Malik Ishaq, the leader of Lashkar-e-Jhangvi (LJ), was held on Friday after two recent bombings in the southwestern city targeting the Shiite Hazara minority killed more than 180 people, sparking nationwide protests.

The outlawed militant group, linked to both Al-Qaeda and the Pakistani Taliban, claimed responsibility for both attacks.

"We have always been demanding arrest of all those involved in any act of sectarian violence, irrespective of their party affiliation," said Abdul Khaliq Hazara, leader of the Shiite Hazara Democratic Party.

"Ishaq must be brought to justice and punished for involvement in violence," he added.

Ishaq, who has been arrested before, was released by a court on bail in July 2011, even though he has been implicated in dozens of murders.

He was detained briefly in 2012 for inciting sectarian hatred and has also been accused of masterminding the 2009 attack on the Sri Lankan cricket team in Lahore, which wounded several players and killed eight Pakistanis.

His latest arrest -- which came a day after the Pakistani army denied any links to LJ -- should not be an "eye wash", said Sajid Naqvi, another Shiite party leader.

"We demand his trial and the authorities should provide protection to witnesses who would like to appear in the court," he said.

Shiites, who make up around 20 percent of the mostly Sunni Muslim population of 180 million, are facing record numbers of attacks, raising serious questions about security as nuclear-armed Pakistan prepares to hold elections by mid-May.

The February 16 bomb attack in Quetta killed 89 people, while 92 people were killed in an attack at a Hazara snooker hall on January 10.

Protesters poured onto the streets following the latest bombing and shut down parts of Karachi, Lahore and Islamabad, demanding better protection for Shiites and lashing out at the government for failing to catch the perpetrators.

Officials said earlier this week that security forces had killed four men and detained more than 170 alleged suspects.

LJ emerged as a spin-off from mujahideen groups which were funded by the US Central Intelligence Agency and backed by the Pakistani intelligence services during the 1980s war against Soviet troops in neighbouring Afghanistan.