Mr Lopez Obrador said he wanted to reach an agreement with the governments and companies in the US and Canada to develop Central America and southern Mexico, so people wouldn't have to emigrate — “to address in that way — and not with coercive measures — the migration phenomenon.”

Mr Lopez Obrador was clear in blaming extreme market-oriented policies he calls neoliberalism for Mexico's problems.

“Mexico's crisis originated not only with the failure of the neoliberal policies applied over the last 36 years,” he said in his inaugural speech, “but also in the prevalence of the filthiest corruption.”

The rowdiest response from Congress came when Mr Lopez Obrador pledged “not to persecute officials of past administrations,” saying “revenge is not my strong suit.”

Combined with a deep sense of nationalism and his own place in history, Mr Lopez Obrador's inauguration is the most home-grown, populist handover of power in decades.

As to underscore the transition, British Labour Party leaders Jeremy Corbyn showed up for inauguration after visiting Lopez Obrador a day earlier at his house in southern Mexico.

“At a time when the fake populists of the far right are gaining ground internationally — including in Latin America,” according to a Labour Party statement issued in London, Mr Lopez Obrador “has shown that a progressive agenda for change can win power and take on the status quo.”

Mr Lopez Obrador pledged to personally oversee daily 6:00am security briefings to confront the rising tide of violence in Mexico, and pledged to ban both oil and gas fracking and genetically modified crops.

Mr Lopez Obrador will hold another ceremony later in the day on Mexico City's main square, where a leader of Mexico's indigenous communities will bestow a traditional symbol of authority — a ceremonial wooden staff. A grand celebration featuring traditional music will be held in the square.

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The country's 65-year-old new leader is moving the presidential office fully back to the centuries-old National Palace that lines one side of the square, while refusing to live at the luxurious, heavily guard presidential residence 6 miles (9 kilometers) to the west. He will reside instead at his private home.

Closed to the public since the first parts were built in the 1930s, the compound will now be used for public events and it was thrown open to the public on Saturday.

Gabriela Barrientos, 71, a retired secretary and Jesus Basilio, a market vendor, 55, were among the first to line up at the gate to enter what Basilio called “the house of the people, an emblematic place we will be able to enter for the first time.”

The handover of power began at midnight when new cabinet secretaries were sworn in for key security posts — a tradition meant to ensure there's always someone at the helm of the Army, Navy and Interior Department, the country's top domestic security agency.

New Interior Secretary Olga Sanchez Cordero said in a post-midnight ceremony that the new government will “listen to everybody, the majority and the minorities, because in a democracy all opinions can be expressed.”

Mr Lopez Obrador gained prominence as a leftist politician leading protests against oil pollution in his swampy native state of Tabasco, though he hasn't given any indication that he will cancel private oil exploration contracts or pull out of Mexico's free trade agreements with 44 countries.

Mr Lopez Obrador won a crushing victory in the 1 July elections after two previous, unsuccessful runs for the presidency and he is the country's first president since the Mexican Revolution to rise to prominence as a protest leader.

He sees his inauguration as a historic “fourth transformation” of Mexico, following independence from Spain, the liberal reforms that broke the church's dominance in the 1850s and the 1910-1917 revolution.

His predecessor, Enrique Pena Nieto, leaves office with a historically low approval rating, which in several polls ranged from 20 per cent to 24 per cent. Mr Pena Nieto failed to rein in Mexico's rising homicide rate or deal with thousands of Central American refugees and migrants camped out on the border, leaving both intractable issues as the biggest immediate challenges facing Lopez Obrador.

Associated Press