Political gatherings have been banned in two Pakistani provinces and many activists arrested to prevent them joining a planned protest march.
Opposition supporters and lawyers had organised what they are calling a "long march" against the government due to start later this week.
Activists, lawyers and ordinary citizens have reacted to the latest developments with a mixture of defiance and fear.
BLOGGERS AND ACTIVISTS MOBILISE
As political tensions escalate in Pakistan, many bloggers have turned their efforts to providing live updates for citizens concerned about the situation.
The long march live update service compiles the latest news reports with comments and messages from people directly affected by the security measures.
Blogger Awab Alvi who publishes his, Teeth Maestro blog from Karachi, says he set it up because he felt the public needed one place where everything could be viewed and where information could be shared.
"We have people contributing key bits of information from news reports and people reporting from the ground... I got an SMS from one guy who was arrested just before it happened. We get information from people in Lahore and Islamabad. There is a lot of frustration out there," he said.
Online activists are encouraging citizens to SMS their experiences and plans to a central number and their messages will be posted on a designated protest website.
Pakistanis are also posting their views and their updates on what they call the "long march" on microblogging site Twitter.
Student and social activist Awais Naseer is in Rawalpindi and has been regularly updating people following him on Twitter about the arrests in his hometown and in its twin city, Islamabad.
"I have direct contact with people in opposition political parties and in certain other organisations and the homes of these people, party workers, are being raided," he told the BBC News website.
Also in Rawalpindi, political activist Faris Kasim said that he still planned to take part in the rally.
"We may not be able to gather now but we are keeping in touch through SMS. I have an air ticket for Lahore and I will leave for Islamabad.
"I don't think us citizens will be targeted unless we were part of a big crowd. I know it can get dangerous," he said.
People across Pakistan have emailed the BBC with their concerns about the latest developments.
Lubna Hassan was planning to attend the protest
Lubna Aisha Hassan in Karachi says she fears these measures are reminiscent of the days of military rule.
"Today they have introduced measures in Sindh. I'm not taking part in the protests now because it is too risky at the moment... it would be too dangerous for people to do things here.
"I don't know how bad it will get, but we expect the worst," she says.
Student Syed Haris had been planning to take part in the protests but the latest measures have made him think twice.
"We were going to take part in the protest, but we will not now. I'm a student and I cannot afford to be put into jail. The government is creating instability but we are all kind of scared now."
A few of those who contacted the BBC believed the planned marches were part of the problem and would only lead to the destabilisation of the country.
But some lawyers in the provinces affected by the ban on political gatherings have said they plan to go ahead with their protest.
Police have arrested many opposition activists in Pakistan
Sardar Tariq Hussain, joint secretary of the Rawalpindi High Court Bar Association, said that he and his colleagues were still determined to protest for the reinstatement of the judges sacked by former President Musharraf.
"The government has tried to put pressure on us and arrest some of our colleagues," he said.
"Today we came out in great strength and we protested around the city. We will break the orders. Many of us are keeping away from our own houses because we know they are actively trying to arrest the lawyers actively participating in this movement."
But in Lahore, the mood of lawyer Saad Amir was more cautious.
"I was planning on leaving Lahore for Islamabad to take part in the march this Sunday. But I don't know now. I'm just gauging the situation and watching the news to see how it turns out.
"It's getting pretty ugly now," he said.