Independent candidate Nicusor Dan was sworn in as Romania’s new President on Monday in a formal ceremony at the country’s Parliament.

In his inaugural speech, the 55-year-old leader called for “fundamental change” while pledging to uphold the rule of law. He urged citizens to keep “positive pressure” on state institutions to push for reforms and vowed to remain responsive to the public.

“Romanian society has proven itself to be alive and strong. I will be a President open to the voice of society,” Dan said.

Dan won the presidential runoff on May 18 with 53.6% of the vote, defeating George Simion, leader of the nationalist Alliance for the Union of Romanians.

Following his swearing-in, Dan proceeded to Cotroceni Palace to formally take over from interim President Ilie Bolojan.

Romania’s Constitutional Court had officially confirmed Dan’s victory last week and dismissed a legal challenge by Simion, who had alleged election irregularities.