Pakistan riot police detained dozens of activists outside the country's Supreme Court on Monday, as part of a growing crackdown on opponents to President Pervez Musharraf's bid for re-election.
The US Embassy says the crackdown on the opposition is "extremely disturbing" and has called for the release of those arrested.
Since Saturday, authorities in Pakistan have been detaining opposition activists as the Supreme Court finishes its review of legal challenges against General Musharraf.
The petitions argue that the president's dual role as military chief and political leader is unconstitutional, and that he is not eligible to run for re-election.
Mr. Musharraf says he will step down as military chief if he is re-elected as president on October sixth. In Pakistan, a president is elected by its national and provincial assemblies, not by a direct public ballot.
Earlier on Monday, the court dismissed two of seven legal challenges. A final ruling on the remaining cases is expected Tuesday or Wednesday.