A man with a loaded gun has aimed it at Argentina’s Vice President Cristina Fernandez de Kirchner – only for her to be left unharmed as it failed to go off.

The attack on Friday (Australian time) underscored rising political tension in Argentina and around the region that has put politicians on edge from Colombia to Brazil.

“A man pointed a firearm at her head and pulled the trigger. Cristina is still alive because, for some reason yet to be confirmed, the gun … did not fire,” President Alberto Fernandez said in a televised address on Thursday.

Mr Fernandez said the gun was loaded with five bullets.

“This is the most serious event we have gone through since Argentina returned to democracy,” he said.

Ms Fernandez de Kirchner is on trial on corruption charges and the attack happened as hundreds of supporters gathered outside her Buenos Aires home.

Video footage showed a man holding a pistol centimetres from her head as she greeted supporters.

The assailant, who authorities identified as a 35-year-old Brazilian man, was quickly arrested by police and the weapon seized.

Ms Fernandez de Kirchner, who was president for two terms between 2007 and 2015, is a divisive figure in Argentina. She could face a 12-year sentence and possible disqualification from public office over public contracts awarded in the early 2000s.

She has been widely expected to run for the Argentine Senate and possibly the presidency in next year’s general elections.

“When hate and violence prevail over debate, societies are destroyed and situations like these arise: attempted assassination,” said Economy Minister Sergio Massa on Twitter.

Heads of state and political allies from around the region, including Chilean President Gabriel Boric, Venezuela’s Nicolas Maduro, Peru’s Pedro Castillo and Brazilian presidential candidate Luiz Inacio Lula da Silva denounced the attack in messages on Twitter, expressing solidarity with Ms Fernandez de Kirchner and relief that she was not hurt.

-AAP