His inauguration was being attended by regional leaders, although not by outgoing President Alan Garcia.

Mr Humala defeated right-wing candidate Keiko Fujimori in June's second round.

Once a fiery nationalist, Mr Humala says his approach is now of the moderate left, modelled on Brazil's ex-president Luiz Inacio Lula da Silva.

Mr Garcia left the presidential palace, handing over the sash for his successor.

Mr Humala, 49, inherits a more prosperous Peru but faces a range of challenges.

In his first address as president, he vowed to keep existing free-market economic and trade policies intact, to provide a minimum pension for all Peruvians over 65 and to raise the minimum wage.