Chile's former dictator Augusto Pinochet, 91, suffered a heart attack Sunday and was taken to a military hospital, an official statement said.
A medical bulletin described Pinochet's condition as "serious but stable".
It said his heart was not working sufficiently and that his lungs were also affected.
On Nov 25, Pinochet, who ruled from 1973-90, marked his 91st birthday, with a group of supporters gathering outside his home here to congratulate him.
Last Monday, a fourth set of human rights violation charges were pressed against Pinochet, and he was put under house arrest.
The charges concern the murders carried out by the so-called caravan of death, the Chilean army squad that executed some 70 people soon after the September 1973 coup that brought Pinochet to power.
He has been also charged with crimes committed at the former torture site Villa Grimaldi and for the Operation Colombo involving the cover up of murders of political opponents.