Chavez has been fighting an unspecified type of pelvic cancer since June 2011 and has undergone repeated surgeries, chemotherapy and radiation treatments. The government said in its last update on Monday that Chavez was in a "stable situation" while being treated for a severe respiratory infection. The government has hasn't said how severe his "respiratory deficiency" is.
Militia troops in uniform gathered by the hundreds near the presidential palace. National Guard soldiers and police stood guard on street corners while hip-hop artists performed on stages set up along the avenue leading toward the presidential palace.
It was one of the largest rallies for Chavez in recent years. Public employees joined the president's supporters, and some arrived in government buses from across the country.
Many in the crowd held up posters reading: "Now with Chavez more than ever."
"We're Chavez. Chavez is now an ideology," said Elio Silva, a member of the radical Tupamaro grassroots group who traveled five hours by bus for the event. He wore a black beret with a single star, a style once worn by Argentine revolutionary Ernesto "Che" Guevara.
Silva said he holds out hope that Chavez is recovering, and said he is sure that whatever happens in the weeks to come, "it will all be democratic."
Vendors sold caps and shirts with images of Chavez. Some wore felt hearts in the colors of Venezuela's flag pinned to their shirts, with pictures of Chavez pasted atop the hearts.
In a remark that echoed the sentiments of many in the crowd, teacher Marcelo Villegas said: "Unfortunately, Chavez can't be with us today. But we the people represent Chavez. He is and always will be our leader."
Associated Press writers Fabiola Sanchez and Vivian Sequera contributed to this report.
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