Jailed opposition leader Leopoldo Lopez has begun a hunger strike and is calling for a mass anti-government protest next weekend.

The former Caracas area mayor accused authorities in a video leaked to news media on Saturday of killing dozens of people during 2014 protests. More than 40 deaths on all sides were reported in those demonstrations.

Lopez has been held in a military prison for more than a year on charges related to his role in leading last year's protests against the South American country's socialist administration.

The video leak came after news broke that fellow opposition Daniel Ceballos was being removed from the military prison outside Caracas where he was held with Lopez and transferred to a public jail away from the capital.

U.S. Assistant Secretary of State Roberta Jacobson said on Twitter late Saturday that she was "worried" about Ceballos' transfer without a judicial order and called on the government of President Nicolas Maduro to "release all political prisoners."

Ceballos' transfer comes amid worsening economic problems in Venezuela, including the national currency's loss of a quarter of its value over the last week.

In the video, Lopez repeated his charge that Venezuela's government is corrupt and incompetent.

"One year and three months after our call for change, the situation has gotten even worse. More lines, more inflation, more scarcity, more crime, more corruption," he said, standing before what looks like a metal door in a mostly bare white room.

Lopez called for big, peaceful demonstrations next Saturday. He also announced he and Ceballos were starting a hunger strike to demand the release of political prisoners and an end to government repression, as well as to a set date for legislative elections that the administration has promised to hold sometime in November or December.

Venezuela's ombudsman, Tarek William Saab, said on Twitter that he met Saturday with Lopez. He said the opposition leader had been disciplined after a mobile phone was found in his cell in violation of prison rules, the third discovered in the cell in four months.

Ceballos' legal team said earlier that he had phoned his mother before dawn Saturday to say he had been moved to one of Venezuela's most violent penitentiaries, in the town of San Juan de los Morros.

That was later denied by Saab, who said he met with Ceballos at a different, recently opened jail in the same town. In messages posted on Twitter, Saab said Ceballos is in good health and the ombudsman's office will continue monitoring his conditions in confinement.

Ceballos was removed as mayor of the western city of San Cristobal during last year's anti-government protests. It was unclear why he was transferred to a regular prison.

The move comes less than a week after Ceballos won from behind bars a primary in San Cristobal to stand as a candidate for the opposition alliance in this year's legislative elections. Under Venezuelan law, a win in the general election could free him from jail because legislators receive immunity from prosecution during their terms.

Ceballos was arrested in March 2014 and quickly convicted on charges of disobeying authority for his refusal to remove barricades demonstrators erected in San Cristobal. Although he completed that one-year sentence, he was ordered held pending trial on more serious charges tied to his support for protests in the city, which kicked off a nationwide wave of anti-government unrest.