As twin protests in Pakistan's capital enter a fifth day, demonstrators are planning to march on Islamabad's Red Zone in a bid to bring down Prime Minister Nawaz Sharif.
On the eve of Tuesday's march, police conducted an arrest sweep in the eastern province of Punjab to prevent supporters of the protest leaders to join protests. About 150 supporters of protest leaders were detained overnight, according to police.
Opposition leader Imran Khan and anti-government cleric Tahir ul-Qadri have led thousands of supporters from Punjab to Islamabad, accusing Sharif of vote rigging and corruption.
The government has said Khan and Qadri are free to demonstrate peacefully but will not be permitted to enter the Red Zone, which is home to many Western embassies, the Supreme Court and government ministries.
Al Jazeera's Kamal Hyder, reporting from Islamabad, said Khan had imposed a deadline of 6pm local time [13:00 GMT] as the start of his supporters' march on parliament.
"He has said already this will be a peaceful march and none of his people will resort to violence," our correspondent said.
"There is a lot of tension and apprehension in case struggles do break out. Imran has said the police will not shoot him and that he has the right to march on parliament."
Khan told Al Jazeera on Monday the march would take place at any cost - even if it cost lives.
Qadri has said he will meet his supporters later on Tuesday to consider whether to march alongside Khan.
Their protests have so far remained separate because the two have different supporters and plans for what should happen if Sharif steps down.
The Red Zone has been sealed off with shipping containers and barbed wire, and is guarded by thousands of riot police and soldiers.
Any attempt by protesters to force their way in could lead to a violent confrontation.
The protests have added pressure to the 15-month-old civilian government already struggling to overcome high
unemployment, daily power cuts and Taliban attacks.