Rodrigo Duterte has been sworn in as president of the Philippines, with some hoping his maverick style will energize the country but others fearing he will undercut one of Asia's liveliest democracies amid threats to kill criminals en masse.

Duterte, a 71-year-old former prosecutor and longtime mayor of southern Davao city, won the election in May in his first foray into national politics.

He took his oath of office Thursday to start a six-year term.

Duterte captured attention with promises to cleanse the poor Southeast Asian nation of criminals and government crooks within six months, an audacious pledge that drew support from crime-weary Filipinos but alarmed human rights watchdogs and the dominant Roman Catholic church.