Venezuelan oil minister sitting in for President Chavez at Mercosur summit in Brazil

The Venezuelan oil minister is sitting in for President Hugo Chavez at a gathering of South American leaders in the Brazilian capital.

Brazil's foreign ministry says that Rafael Ramirez will represent Venezuela at the meeting of leaders of the Mercosur trade bloc. The presidents of Brazil, Argentina and Uruguay are also attending.

Chavez's absence at the meeting has raised new questions about his health.

The president returned to Venezuela on Friday after 10 days of medical treatment in Cuba, where he underwent hyperbaric oxygen treatment. Chavez has spent much of the past 18 months under treatment for cancer and has said he's free of the disease

Friday's meeting is the first since Venezuela became a full member of Mercosur in July.