Sharjah24 – AFP: Gustavo Petro on Sunday took the oath of office as Colombia's first-ever leftist president, before a crowd of hundreds of thousands at his inauguration in Bogota.

The 62-year-old former guerrilla and onetime mayor takes over from the deeply unpopular Ivan Duque, with plans for profound reforms in a country beset by economic inequality and drug violence.

Petro's hard-fought victory in June elections brought Colombia, long ruled by a conservative elite, into an expanding left-wing fold in Latin America.

"I swear to God and promise the people that I will faithfully enforce the constitution and the laws of Colombia," said Petro before the large crowd of supporters gathered in Bogota's Bolivar Square.

Petro -- whose government should enjoy support from a left-leaning majority in Congress -- called in his inaugural address for Colombian armed groups to "lay down their arms" and accept legal benefits "in exchange for peace."

He also took aim at decades of counter-narcotics efforts, saying: "It is time for a new international convention recognizing that the war on drugs has failed."

And he called for the creation of an international fund to help the deforestation-plagued Colombian Amazon.

On the campaign trail, Petro had promised during his four-year term to raise taxes on the rich, invest in health care and education, and reform the police after a brutal crackdown on anti-inequality protests last year that was internationally condemned.

Maduro congratulated Petro on his inauguration, saying in a video: "I extend my hand to the people of Colombia, to President Gustavo Petro, to rebuild brotherhood on the basis of respect and love between peoples".

The Venezuelan leader had not been invited to the ceremony by outgoing president Duque, whose office oversaw preparations for the event.

Duque had also denied a request by Petro to have the sword of revolutionary figure Simon Bolivar present at the ceremony -- a decision the new president quickly reversed right after taking his oath.