CARACAS, Venezuela — ­Venezuela’s embattled president, Nicolás Maduro, faced challenges on multiple fronts Saturday, as massive anti-government rallies choked the streets, a top general defected and the opposition urged European powers to join the international alliance against him.

The dramatic events underscored the pressures mounting on Maduro. They also suggested the strategies ahead for opposition leader Juan Guaidó — an untested 35-year-old industrial engineer — as he tries to expand Maduro’s global isolation and appeals for the support of more Venezuelans.

Guaidó, who heads the opposition-controlled National Assembly, has won the backing of the United States and a host of other nations since declaring Maduro a usurper and himself interim president.

Across the nation, huge numbers of protesters — possibly hundreds of thousands — took to the streets. 

The outpouring appeared to be one of the largest demonstrations ever against Maduro and the deep crises facing Venezuela under his leadership. Hyperinflation and shortages of food and medicines have fueled hunger, diseases and a historic outflow of migrants.

“We are marching because we can’t take this situation anymore,” said Carmen Sanchez, 42, who lives in the slum of Petare and joined a protest in Caracas that stretched for many city blocks and onto the balconies of buildings.

“We don’t have enough money for food. This government has to resign for Venezuela to be beautiful again, and I have faith Guaidó will bring us success,” she said.

The demonstrations alone were unlikely to cause Maduro to buckle. But opposition leaders also hope large-scale protests — in combination with international isolation and sanctions — will push Maduro to negotiate his exit or prod the military to force him out.

Maduro, however, was already hit by a blow from within: A senior figure in the armed forces broke publicly from the government. It marked the most serious act of dissent yet from the military brass, which has stood as Maduro’s main bulwark against the opposition.

In a video circulating on social media Saturday morning, an acting Venezuelan air force general, Francisco Yanez, denounced the “dictatorship” of Maduro and recognized opposition leader Guaidó’s claim as the nation’s legitimate interim leader. 

“People of Venezuela, 90 percent of the armed forces are not with the dictator,” Yanez, in uniform, said in a video that he appeared to have filmed himself. “The transition to democracy is imminent.” 

The Twitter account of Venezuela’s air force, which consistently retweets Maduro and other government officials, released a photo of the video with the word “traitor” in red letters scrawled over Yanez’s face. 

“We have to highlight that he has no command over troops and less so over air force units,” an air force tweet said. “He has no leadership at the air force and was only serving planning functions.”

For the opposition, the massive protests on Saturday marked a key step forward in its ability to sustain a social uprising against Maduro. The anointed successor of leftist Hugo Chávez, who died in 2013, Maduro was sworn in for a new six-year term last month following elections internationally derided as fraudulent. 

Guaidó has invoked constitutional powers declaring himself the nation’s rightful interim leader, setting up a global power play that has seen Russia and Cuba back Maduro while a growing number of Western nations back Guaidó. 

In an attempt to rally his side, Maduro brought supporters onto the streets for counterprotests, to mark 20 years of socialist rule.

Guaidó, speaking to the masses in a hoarse voice, appealed to “Chavistas” — those who have long supported Chávez.

“I want to send a message to the Chavista people,” Guaidó said. “You believed in a project, and now you’ve been disappointed.

“The military and the world take note,” he added. “There are many, many people filling the streets of Venezuela today. This movement is historic, and unstoppable.”

At the smaller pro-government rally, meanwhile, people in the crowd shouted, “Prison for Guaidó!” Maduro suggested that he still has moves to make.

“Everything at its right time,” he told supporters. “We know what we have to do in every moment. Justice sometimes takes time, but it comes.”

Maduro also called for new elections for the opposition-
controlled National Assembly. Stripped of its power in 2017 by the government, the body has nevertheless continued to meet, and Guaidó’s constitutional claim as interim leader is based on his being the elected head of the chamber.

Although official media did not broadcast the protests, government forces appeared to be using relative restraint in crowd control, though some melees were reported among small groups of protesters and security forces. A video circulating on social media showed a national police officer in the city of Barquisimeto, about 220 miles west of Caracas, telling protesters that he would not use violence against them. One protester was shown hugging the guard. 

Sanchez said recent raids by security forces in Petare have been terrifying. “Last week was horrible. They took kids from their homes. We were all threatened,” she said.

The pro-government demonstration in central Caracas had drawn about 300 people by 10:30 a.m. Dressed in red and carrying ruling party flags, they were marching toward the presidential palace.

“Our people, once again, overflowing this avenue,” Maduro said, addressing his supporters. “Those who accuse us of being a dictatorship must know that since the foundation of the revolution, we have become a profoundly free and democratic people. Venezuela will never have a dictatorship.”

On Saturday, Guaidó outlined a plan to ship humanitarian aid into the economically shattered country. He announced three staging areas, on Venezuela’s borders with Colombia and Brazil and on one nearby Caribbean island.

Maduro has resisted allowing in international aid, and Guaidó has hoped to use caravans of food to challenge the military and government’s will. U.S. national security adviser John Bolton tweeted that the United States would back the effort. 

“It will be a dilemma for the officers,” Guaidó said. “You, generals, will decide.”

The Trump administration has said no options are “off the table” as it seeks to pressure Maduro to resign. U.S. officials in the past week threw up new sanctions that effectively cut Maduro off from Venezuela’s most important foreign revenue stream: oil sales to the United States. 

Maduro successfully rode out four months of protests in 2017 after an iron-fisted response left more than 100 dead. Since protests restarted two weeks ago, the government has unleashed another wave of repression that has left at least 35 dead and 850 detained. 

The defection of Yanez, the air force general, suggested new cracks in the military hierarchy that has previously proclaimed steadfast loyalty to Maduro.

Antonio Rivero, a former Venezuelan general now living in exile in Miami, said that Yanez did not appear to command a large contingent of troops and that his strategy remained unclear — as did his current whereabouts.

“For now, I see him isolated. He doesn’t have a division behind him,” Rivero said. 

On Jan. 21, a group of national guard soldiers took to the streets of a western Caracas slum and filmed themselves calling people to the streets. They had taken weapons from a military unit. But the small insurrection was quickly quashed, and 27 soldiers were jailed. 

 Maduro has called for dialogue with the opposition, saying he is willing to meet Guaidó “wherever, whenever, he wants.” But the opposition, which has engaged in fruitless roundtables with the government before, has seen the offer as a ruse to buy time. 

Faiola and Krygier reported from Miami.