Rodrigo Duterte has been sworn in as the 16th president of the Philippines in front of an audience of 600 guests and millions more watching on television and online, crowning a rise from little-known mayor to leader of a huge nation.

His youngest child by his side holding the family Bible, Duterte was sworn in at noon on Thursday (04:00 GMT) in Manila, declaring before a Supreme Court justice that he would "preserve and protect" the constitution, which analysts say will likely see major changes during his six years in office.

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"True change is the mandate of my government," Duterte said in his inaugural speech.

"I was elected as president to serve the entire country. I serve everyone. But not only one."

On his campaign promise to solve crime and drug abuse problem, Duterte said the fight "will be relentless and it will be sustained".

But he also said he knows "the limits of the power and authority of the president", adding "I know what is legal and what is not". During the campaign he had threatened to shoot criminals and kill drug dealers.   

The 71-year-old broke with tradition by taking his oath at the Malacanang presidential palace, instead of hosting an inaugural rally, which he said would only cause traffic jams in the already congested streets of the capital.

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In a nod to his millions of followers on social media, Duterte's inauguration was broadcast online using Facebook Live, allowing Filipino workers abroad, who overwhelmingly voted for him, to witness the event.   

'An authentic leader'

Duterte brings to the presidency more than two decades of experience as a mayor seen as having cleaned up Davao, a major city in Mindanao once described as the Philippines' "murder capital".

In three decades in politics, he has never lost an election. He is also the first city mayor to be elected president without previously having held a national position.

"I think this is a fresh change," Jenny Lind Elmaco, a Manila-based political observer and women's rights advocate, told Al Jazeera.

"Duterte is an authentic leader. He does not hide behind pleasantries, sugar-coat his opinions or mince his words." 

Still, given controversial pronouncements that he would like to see all drug criminals dead, some are concerned about how he will use his power to fight crime. 

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"I believe we all need to be optimistic about his leadership. But we also have to be vigilant. Governance is too important to be left only to government," Elmaco, executive director of the women's group SPARK, said.

Record growth

During the campaign, Duterte vowed to amend the constitution and support federalism, which he said would help to end a Muslim rebellion in the country's south.

With a promise to break apart what he called the domination of "Imperial Manila", Duterte now faces the challenge of building on strong economic growth while fulfilling his promise to fight corruption and end crime.

Under his predecessor, Benigno Aquino, the country achieved record growth, but at least a third of the population live below the poverty line.

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Jose Torres, director of the National Press Club of the Philippines, told Al Jazeera that the benefits of economic growth were "not really felt" by the poorest.

He said Duterte was "able to take advantage of the despair of the poor and the middle class" towards the ruling class.

A problem for Duterte, however, is that he has overpromised, Torres said.

"My only hope is he will be able to fulfill at least 25 percent of what he promised."

Source: Al Jazeera