Where is Argentina's president?

Argentine President Cristina Fernandez de Kirchner hasn't made a public appearance for nearly a month, prompting speculation about her health. She's not the first world leader to go off the grid. Check out some others:

Algerian President Abdelaziz Bouteflika suffered a ministroke in April and hasn't appeared as much in public since then. State media reported on January 14 that he's in Paris for a routine checkup and that his health is improving.

As he battled cancer, Venezuelan President Hugo Chavez flew to Cuba for treatment and stopped his once-frequent TV appearances. He died in March at 58.

Pregnancy rumors swirled when North Korean first lady Ri Sol Ju disappeared for months in 2012. Officials never announced whether the rumors were true. But former basketball star Dennis Rodman has called President Kim Jong Un a "good dad" and said he cradled the couple's baby girl last year.

Rumors about health problems, car crashes and even assassination surged when China's then-Vice President Xi Jinping disappeared from public in 2012. Xi, now China's President, reappeared two weeks later.

When Syrian Vice President Farouq al-Sharaa wasn't seen publicly in August 2012, rebels claimed he'd defected. But al-Sharaa resurfaced at meetings in Damascus more than a week later, making it clear that he hadn't left the government.

Former President John Atta Mills of the West African nation of Ghana scaled back public appearances and made a medical trip to the United States shortly before he died in July 2012.

Former Nigerian President Umaru Musa Yar'Adua went to Saudia Arabia to be treated for inflammation of tissue around his heart in 2009. No further news came from him until almost two months later, when he gave the BBC an interview from his hospital bed. He died several months later.

• It's been nearly a month since Argentine President Cristina Fernandez de Kirchner's last appearance
• Critics question who's in charge of the South American country
• Fernandez's aides dismiss concerns, stressing she's the one making government calls
• Fernandez went on medical leave in October so doctors could remove a blood clot from her brain's surface

Buenos Aires (CNN) -- Argentine President Cristina Fernandez de Kirchner is no wallflower when it comes to public speaking.

She's known for passionate proclamations on national television and rapid-fire online posts about her work.

But it's been almost a month since her last public appearance and 33 days since her last Twitter post, prompting critics to question who's in charge of the South American country. Close aides to Fernandez have dismissed such concerns, stressing that she's the one making the government calls.

"The President is present every day, working with us," Cabinet Secretary Jorge Capitanich told reporters earlier this month, according to the state-run Telam news agency.

Fernandez went on medical leave in October so doctors could perform emergency surgery to remove a blood clot on the surface of her brain. She officially returned to work in November and appeared at a series of events in December.

But now, with Fernandez largely out of public view once again, speculation has surged about her whereabouts, and her health.

"If we hadn't had the President's illness just a few months ago, one would discard it. But the problem is the rumor has been established, and the sense of uncertainty of not knowing why," said Orlando D'Adamo, director of the Center of Public Opinion at the University of Belgrano in Buenos Aires. "Is it a political strategy? Is she making room for a new candidate for 2015? Is it because she does not want to face difficult situations for the government? We do not know."

Others think Fernandez is taking a break to take care of her health and not face a similar fate as her husband, former President Nestor Kirchner, who died in 2010 after suffering a heart attack.

"I think she does not want to repeat that story," said Enrique Zuleta, another political analyst.

As Argentina has faced high inflation and other challenges in recent weeks, Capitanich was the public face of the government.

On the streets of Buenos Aires, residents say they have felt the President's absence.

"There are many problems that require a solution, and there is no clear response from her," worker Gabriel Blanco said.

Merchant Nelida Jorquera said she was worried about the situation.

"But I think she is a serious person, and she would not deceive the people," she said.

CNN's Jose Manuel Rodriguez reported from Buenos Aires. CNN's Catherine E. Shoichet reported from Atlanta.