"We have been able to confirm that 43 opposition members have been detained -- 10 women and 33 men -- in a crackdown on Monday in the Santiago de Cuba area. All remain under arrest," said Elizardo Sanchez, head of the outlawed but tolerated Cuban Human Rights and National Reconciliation Commission.
The commission on Monday reported 25 detentions but its figure on detentions near Santiago de Cuba -- Cuba's second-largest city -- has kept rising.
"Almost all of the detainees are members of the Patriotic Union of Cuba," an opposition force led by former political prisoner Jose Daniel Ferrer. He was arrested on Monday along with his wife Belkis Cantillo, at their home in Palmarito de Cauto, near Santiago.
Ferrer, who was among 75 dissidents arrested in a 2003 crackdown and released last year after a mediation effort by the Roman Catholic church, had his telephone line cut as well, according to activists.
Sanchez said the Cuban secret police on Monday launched a "wave of repression" with the arrests, following up on dozens of detentions of opponents just ahead of a landmark visit last week of the pope.
The United States, which has tense relations with Cuba, said it was "extremely concerned" about the latest detentions and what it said were efforts to silence reporting by cutting off activists' cellular and Internet services.
"We call upon the Cuban government to release all peaceful civil society activists immediately," State Department spokesman Mark Toner told reporters in Washington.
"We particularly condemn that most of those arrests took place during the pope's visit and with the aim of preventing those arrested from attending public masses that the pope officiated," Toner said.
While in Cuba, the pontiff did not meet with opposition members. But last Wednesday he wrapped up a visit to Cuba with a call for respect of "basic freedoms," pursuing his persistent prodding of the island's communist authorities to embrace change.
"May no one feel excluded from taking up this exciting task because of limitations of his or her basic freedoms," Benedict said at a mass in Havana, as President Raul Castro looked on. Cuba is the Americas' only one-party communist regime.
Last week, dissident sources said Cuban authorities rounded up at least 150 to thwart any demonstrations during a landmark visit by the pontiff.