The United States has spoken out about Monday's arrest of dozens of opposition activists in Pakistan Monday, after they demonstrated outside the country's Supreme Court.

U.S. Secretary of State Condoleezza Rice told the Reuters news agency late Monday the arrests are troubling, and added that Washington has communicated the concern to the Pakistani government. Earlier in the day, the U.S. Embassy in Pakistan said the move was "extremely disturbing" and called for the release of those arrested.

Since Saturday, authorities in Pakistan have been detaining opposition activists as part of a growing crackdown on opposition to President Pervez Musharraf's bid for re-election. Activists are protesting outside the Supreme Court as it 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 6. In Pakistan, a president is elected by its national and provincial assemblies, not by a direct public ballot.

Monday, the court dismissed two of seven legal challenges. A final ruling on the remaining cases is expected Tuesday or Wednesday.

Also on Monday, Pakistan's Supreme Court Bar Association announced its nomination of Justice Wajihuddin Ahmed as a presidential candidate and challenger to Mr. Musharraf.

Government officials say they made the arrests to prevent public protests from getting violent.

Some information for this report was provided by Reuters.