Protesters briefly scuffle with riot police as they massed in Bucharest's University Square.
Tens of thousands of Romanians on Saturday protested against legislation passed by Parliament which critics say will make it harder to prosecute crime and high-level corruption.
Protesters briefly scuffled with riot police as they massed in Bucharest's University Square.
Protesters shouted, "Thieves, thieves!" and "Resign!" and blew whistles and waved Romanian flags. They then marched toward Parliament.
Protesters of all ages came to vent their anger at the left-wing government, some accompanied by dogs or children.
Architect Tiberiu Calinescu, 30, who was carrying his 4-month-old daughter, said, "I have come here for the future of my daughter," adding "I want to live in a Romania that is civilised and close to European" standards.
TRT World's Arabella Munro has this report.
Diana Gradinaru, a 45-year-old economist, said the new legislation could result in "terrible thefts" by high-level officials, citing legislation that meant video and audio recordings could no longer be used as evidence in prosecutions.
There were smaller protests in the cities of Cluj, Timisoara, Constanta, Bacau, Sibiu and Iasi. Protesters began arriving earlier in the capital by train from other Romanian cities and were greeted by people waving Romanian flags.
Last year, Romania saw the biggest protests since communism ended after the left-wing government tried to decriminalise official misconduct.
Parliament last month approved amendments to laws that many say will lead to a backsliding on its anti-corruption fight.
Prime Minister-designate Viorica Dancila supports revamping the judicial system. She is an ally of Liviu Dragnea, chairman of the Social Democracy Party, who can't be premier due to a conviction for vote-rigging.
President Klaus Iohannis, a critic of the amendments, needs to sign them into law.
On Friday, he wrote to the Constitutional Court saying one amendment that would allow public officials to own businesses "diminished the standards of integrity" expected from public officials.