Police in Pakistan have rounded up dozens of opposition party leaders to block a rally against the country's military ruler.
The arrests took place in the eastern city of Lahore.
Tensions soared as police erected barbed wire barricades and blocked all main roads leading to the Mochi Gate Garden park.
Thousands are expected to attend the rally.
Police defended the arrests of members of the Alliance for Restoration of Democracy, arguing that a protest would disrupt law and order in the country.
President General Pervez Musharraf's government has refused to give permission for large demonstrations since January, when Pakistan began to crack down on Islamic extremists.
Mr Musharraf has been holding high-level meetings to muster support for a referendum reaffirming his rule. The ballot would be held sometime before parliamentary elections set for October.
Mr Musharraf will address the nation over state-run Pakistan Television to unveil his future political and national security plans.
"We will defy the ban on rallies," said Mr Misbaur Rehman, a local leader in Lahore.
Those detained include the top leaders of the alliance, which includes the parties of former Prime Minister Benazir Bhutto and former Prime Minister Nawaz Sharif.