CARACAS, Venezuela -- The White House is condemning what it calls "the Maduro dictatorship" over the arrests of two top opposition leaders in Venezuela before dawn Tuesday.

Opposition leaders Leopoldo Lopez and Antonio Ledezma had been under house arrest but security force officers hustled them off to a military prison.

In a statement, the White House calls them political prisoners and says they are "being held illegally by the regime" led by Venezuelan President Nicolas Maduro.

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The statement adds: "The United States holds Maduro - who publicly announced just hours earlier that he would move against his political opposition -- personally responsible for the health and safety of Mr. Lopez, Mr. Ledezma, and any others seized."

It calls for Venezuela's government to immediately free all political prisoners.

Meanwhile, Secretary of State Rex Tillerson spoke at a press briefing Tuesday and stressed that the Venezuelan people should have a "voice in the government they deserve."

"Clearly what we want to see is Venezuela to return to its constitution," Tillerson said. "We are very, very trouble by what we're seeing unfold following the constitutent assembly vote ... but the rearrests of opposition leaders last night is very alarming."

Tillerson added that the situation from a humanitarian standpoint is becoming dire.

"We are evaluating all of our policy options as to what we can do to create a change of conditions to where either Maduro decides he doesn't have a future and wants to leave of his own accord."

Sunday's vote gave Maduro's ruling party nearly unlimited power while the U.S. imposed new economic sanctions on Maduro on Monday.

Maduro has provoked international criticism and enraged his political opponents by pushing for the special assembly to rewrite the troubled South American nation's constitution.

Sunday's election of delegates to the assembly comes after nearly four months of political upheaval that have resulted in more than 100 deaths and left thousands injured and detained.

Protesters like Juan Carlos Gutierrez tell CBS News they were threatened with 10 years in jail if caught marching in the streets.

"We have a little piece of democracy and they kill it -- the government is killing it," he said.