An opposition outcry over a lack of information from presidential aides kept up for a fourth day.
Fernandez, 60, remains hospitalized.
Aides were voluble in comments about the president's health but shy of giving a straight answer, analysts said.
Aides said Vice President Amado Boudou was functioning as acting president but wasn't quite in charge as Fernandez was, and comments from senior government officials failed to quiet opposition criticism.
Cabinet Chief Juan Manuel Abal Medina said Fernandez "continues to be the leader in charge of decision- making," with Boudou "executing" other duties, the Buenos Aires Herald said.
Fernandez underwent surgery Tuesday to treat a subdural hematoma, or brain hemorrhage, usually a bleeding between the skull and the surface of the brain. She was put under intensive care after the operation and then transferred to a special unit.
Officials provided scant information about her condition.
Fernandez was prescribed a month's rest right through Argentina's Oct. 27 mid-term congressional elections, seen by analysts as crucial for the remaining two years of her presidency.
The president has been battling economic problems, labor disputes and political infighting at the same time she has dealt with international creditors from the country's 2002 sovereign debt default and a poor showing at the polls would further weaken her hand, observers say.
Several hundred supporters kept a vigil outside the Favaloro Foundation clinic where Fernandez underwent surgery. Presidential spokesman Alfredo Scoccimarro told people outside the clinic Fernandez was "recovering favorably" and was "in [a] very good mood."
Medina denied allegations that a powerful "inner circle" -- including intelligence officials -- is running the country.
"President Cristina Fernandez makes the decisions because power has been vested in her, and working on her instructions the president's team is governing without any difficulty. It is a very solid team," Medina said.