At least 500 protestors were arrested on Monday, March 29 night during the clashes between them and law enforcement officials in Islamabad. A few of their leaders were also arrested, Dawn online reported. Around 200 people were arrested earlier on Monday.
The demonstrators were protesting the execution of Mumtaz Qadri, who shot dead the then governor of Punjab, Salman Taseer. Qadri was Taseer's personal security officer. The demonstrators demanded that Qadri should be declared a martyr.
On Sunday, a month after Qadri was hanged, the protestors prayed for him in Rawalpindi, and then marched towards Islamabad's Red Zone, breaking barriers erected at Faizabad on the way.
The army has been deployed in Islamabad's Red Zone to prevent the situation from getting out of hand.
The Sunni Tehreek and other religious outfits involved in the demonstrations that began on Sunday evening also want the Sharia implemented in Pakistan, an Islamic republic.
Those who were sitting in protest at D-Chowk and Parade Ground were not arrested, but some of those who left the demonstration were arrested, a source said.
The arrested protestors were kept at different locations, some in police stations, and later moved to jails in districts in Punjab near Islamabad, sources said.
As the arrests were in large numbers, Islamabad police first made sure if a particular jail had enough space to accommodate the arrested before sending them there, the sources said.
The march was the second notable incident of its kind in the garrison city's recent history, after sectarian violence broke over Ashura in 2013.
Police sources said they were kept in the dark by religious leaders who were holding talks with the police and intelligence officials for the past few days over Mumtaz Qadri's chehlum (a day of rites marking 40th day of the death of a Muslim).
The religious leaders said the mourners would remain peaceful and disperse after the 'dua' before Asr prayers, police said.
The district administration presumed that the chehlum would be a quet affair since Qadri's funeral was conducted peacefully despite a huge crowd.
Instead of making security arrangements as they had for Qadri's funeral, police relied on the assurances of religious leaders.
"Around half of the police force was deployed in the city on Sunday compared to the deployments on Mumtaz Qadri's funeral, because we were not expecting that they would march towards Islamabad," a senior official said.
"At one stage, the stock of tear gas shells ran out while trying to disperse religious workers at Shamsabad," the official added.