At least four people were killed and more than 200 were wounded in Venezuela during two days of massive demonstrations in the opposition's latest attempt to oust embattled President Nicolás Maduro, a human rights group said.

The Venezuelan Observatory of Social Conflict wrote on Twitter Thursday that overall, 57 protesters have been killed since the beginning of 2019, including two children and two adults who were killed in the last two days of demonstrations.

"Here are their names," the group said on Twitter, listing all 57 people they said have died.

The group said that at least 239 people had been injured "throughout the country by bullets, pellets and tear gas" during the protests on Tuesday and Wednesday.

The group tweeted earlier Thursday that it had confirmed that 14-year-old Yoifre Hernández Vásquez had been shot and killed during a protest Wednesday in Altamira.

The group also said 16-year-old Yosner Graterol was killed by a bullet during a protest in the state of Aragua.

Late Wednesday night, the group said it condemned the death of Jurubith Rausseo García, 27, who was shot in the head during a protest in Altamira on Wednesday.

And on Tuesday, the group said Samuel Enrique Méndez, 25, was killed during a protest in Aragua, but did not list the circumstances of his death.

Thousands took the streets this week after opposition leader Juan Guaidó's call for massive, peaceful protests and for the military to defect against Maduro.

On Wednesday night, Guaidó told the Fox Business Network, "As long as we are mobilized and united, we are very close to achieving our freedom."

He said he could not give a specific date or time, but said they were working on the "transitional and rebuilding process of democracy."

"We are close to achieving this goal as a country," he said.

Guaidó, the head of the National Assembly, invoked a constitutional provision to claim he was interim president in January, and has drawn the backing of more than 50 countries, including the U.S. But the military has thus far largely remained loyal to Maduro, despite some recent shows of support for Guaidó this week.

After two days of demonstrations that went on for hours by both opposition and pro-government forces, Maduro appeared to be holding onto power Thursday as a massive military revolt never materialized.

Maduro appeared flanked by members of the military Thursday morning at a military base near where Guaidó first issued his call for civilians and the military to join him in demonstrations against Maduro. Guaidó had announced what he called the "final phase" of the operation to topple Maduro in a dramatic video alongside formerly detained activist Leopoldo López and a small group of armed military personnel.

Maduro called for a unity against the "traitors" and those who staged an attempted "coup" against his government and for the military to be "united like never before."

Earlier, the socialist leader said he called for a weekend of "dialogue, action and proposal" to draw up a "plan of change" to rectify "the revolution."

Meanwhile, President Donald Trump said Thursday that "the brutal repression of the Venezuelan people must end and it must end soon."

"This was once one of the wealthiest countries in the world," he said. "We were there to help, and we are here to help."