(CNN) -- Venezuelan President Hugo Chavez vowed on Monday to win the "battle" for his health and said his "return has begun."

He spoke from the balcony of the presidential palace the same day he arrived unannounced in his nation's capital.

Dressed in military fatigues and wearing a red beret, Chavez appeared in good spirits though he kept his speech uncharacteristically short.

"How do I begin this conversation? The return has begun!" he said, to throngs of cheering supporters, who gathered one day before the country is set to celebrate its bicentennial.

The president said he was under the strict supervision of doctors, eating well and exercising.

"We will win this battle for life," he said. "I put myself first in the hands of God, and second in the hands of medical science."

Perhaps tellingly, Chavez also spoke about "stages" of treatment, suggesting the fight for his health could be a long one.

Cheering supporters of Chavez filled the streets around the balcony -- waving flags and pictures of their beloved "comandante."

"Thank you, Fidel! For taking care of him," they chanted.

Chavez, 56, returned to Venezuela unexpectedly early Monday. He had been in Cuba for weeks undergoing treatment after doctors performed emergency surgery. Chavez announced last week that they had removed a cancerous tumor.

He said then he was continuing treatment but did not specify what that treatment entailed, where the tumor was located or when he would return to Venezuela.

Prior to that announcement, the Venezuelan leader had kept a notably low profile in the three weeks since officials announced that doctors operated on him, sparking rampant rumors about his health and the country's political future.

Earlier Monday, the Venezuelan leader said he did not think he would be able to accompany the vice president during official events for the nation's bicentennial Tuesday.

"But I am here, and I will be here with you from my command post in the heart of Caracas, in the heart of Venezuela," he said.

Returning for the bicentennial festivities was "politically irresistible" for Chavez, Michael Shifter, president of the Washington-based Inter-American Dialogue, said before Chavez's speech.

"For him not to be there on July 5 would have just ... heightened some of the uncertainty and would have intensified some of the jockeying and jostling for positions among others within his movement," Shifter said.