Brazil's President Dilma Rousseff has been sworn in for her second term.

Rousseff immediately faces tough challenges after taking the oath of office before congress on Thursday.

She must spark a moribund economy that's seen paltry growth since she first took office in 2011.

She also has to deal with a rapidly expanding scandal over a kickback scheme at state-run oil company Petrobras, with allegations bribes made their way into her Workers' Party campaign coffers and those of allied parties.

The left-leaning Rousseff was re-elected in October in a tight race against a more conservative rival.

It's the seventh consecutive time a directly elected president has started a term in office — something the country hasn't seen in nearly a century.