Cuban journalist Yoani Sanchez said she was put under house arrest and her husband taken into custody ahead of a proposed rally that was the first to test the limits of dissent after the U.S. and Cuba reached a deal to improve ties.

“They took my husband Reinaldo Escobar and Eliecer Avila handcuffed in a police car,” Sanchez, editor-in-chief of online newspaper 14ymedio.com, said in a post on her Twitter account. Avila is another activist. Sanchez said she was forbidden from leaving her home.

Phone calls to Cuba’s international press center seeking comment were answered by an automated operator who said all lines were busy.

The move came as a group of Cuban artists organized a rally for today in Havana using the social media tag #YoTambienExijo, or "I also demand." They said they planned to set up a microphone in Havana’s Plaza de la Revolucion where people would be able to express themselves on any issue for one minute without interruption, they said.

Cuban President Raul Castro and U.S. President Barack Obama on Dec. 17 announced plans to re-establish diplomatic ties, release some prisoners and work to ease a five-decade old embargo. The U.S. protested the detentions today.

“Freedom of expression remains core of U.S. policy on Cuba,” Roberta Jacobson, Assistant U.S. Secretary of State for Western Hemisphere Affairs, said in a Twitter post. “We support activists exercising those rights and condemn today’s detentions.”

Few people showed up at the Plaza de la Revolucion at the time today’s rally was scheduled to take place. Tourists with cameras and two policemen were the most obvious visitors to the square, which is lined by government ministries adorned with metal outlines of guerrilla leader Ernesto “Che” Guevara and former President Fidel Castro.

Some supporters of today’s rally said they were visited by Cuban officials encouraging them not to participate. A Facebook page for the group says misleading text messages were sent claiming the gathering was canceled, without saying who sent them.

Sanchez has drawn tens of thousands of followers through her newspaper, blog and use of social media. Obama responded to Sanchez’s questions in an interview posted on the Huffington Post website in 2009 and she was named among Time magazine’s “100 Most Influential People” in 2008.

Philip Brenner, a professor of foreign policy at American University in Washington, said today’s arrests probably won’t upend the accord between the U.S. and Cuba.

“U.S. policy toward Cuba is now rooted in advancing U.S. interests, not in responding to every Cuban action,” he said via e-mail.