CARACAS (Reuters) - Four people were killed and at least 300 were detained in association with protests and looting that took place during Venezuela’s nationwide blackout, rights groups said on Thursday.

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The OPEC nation suffered its worst blackout in history last week following technical problems that the government of President Nicolas Maduro called an act of U.S.-backed sabotage but critics dismissed as the result of incompetence.

Rights groups Provea and the Venezuelan Observatory of Social Conflict said via Twitter that three people were killed in the central state of Lara and one person was killed in the western state of Zulia. The cause of the deaths was unclear.

Alfredo Romero of rights group Foro Penal said at a news conference that 124 people had been detained in protests over public services since the March 8 blackout and that another 200 were arrested over looting.

The Information Ministry did not immediately respond to a request for comment.

Power has returned to many parts of Venezuela, though service has not been fully restored to scattered areas of the capital Caracas and much of the western region.

Venezuela plunged into a deep political crisis in January when Juan Guaido, head of the opposition-controlled congress, invoked the constitution to assume an interim presidency, arguing Maduro’s 2018 re-election was a sham.

That move has put Venezuela at the heart of a geopolitical tussle, with the United States leading most Western nations in recognizing Guaido as the legitimate head of state, while Russia, China and others support Maduro.

Guaido is scheduled to join a meeting of local residents in the El Hatillo district of the capital of Caracas on Thursday.

The blackout that began a week ago left hospitals struggling to keep equipment running, and food rotted in the tropical heat. The nongovernmental organization Doctors for Health said 26 people died in public hospitals during the blackout.

The western state of Zulia suffered intense looting that hit some 350 businesses.