Tens of thousands of Romanians gathered for a second night of protests in the capital, Bucharest, on Saturday, after 455 people were injured the day before.
Romania's centre-right President Klaus Iohannis, a critic of the government, said he "strongly condemned the brutal intervention of the police, which was disproportionate to the attitude of most demonstrators" but added that "any form of violence is unacceptable".
"The interior ministry must explain urgently the way it handled tonight's events", the centrist leader wrote in a statement posted to Facebook.
Three journalists also said they were roughed up by police.
About 1,000 officers in riot gear intervened to clear the crowds assembled in a central square outside the main government building after some protesters tried to break through the police cordon.
Saturday's protest was largely peaceful after the previous demonstration turned violent and 30 people were arrested.
According to the World Bank, up to a quarter of the Romanian population - between three and five million people - live and work overseas, sending back around $US5bn to one of the EU's least developed countries.
Some of the estimated 3 million Romanians living overseas say they left because of corruption, low wages, and lack of opportunities.
Another police spokesman, Georgian Enache, said "the legitimate state violence", was justified because protesters had been warned several times to leave the square.
People attend a protest in Bucharest, Romania August 10, 2018, in this image taken from social media.
Police came in for criticism after they used water cannon and tear gas on Friday to disperse protesters as tens of thousands rallied to call on the left-wing government to resign.
Protesters around Bucharest's Victoriei Square waved Romanian and European Union flags, shouting "Justice, not corruption!" Among them were a number of politicians, including a senator and 28 mayors.
Mr Iohannis had been under extensive pressure from the PSD government to agree to her removal. The PSD also reportedly threatened to discuss suspending him if he put the move off any longer.
Critics say Romania has lost ground in fighting corruption since the ruling Social Democratic Party assumed power in 2016. The changes are being challenged in the constitutional court.
Before Kovesi's sacking, thousands of protesters took to the streets in support of her. It was believed to be the largest demonstration in decades.
After Iohannis criticized the police response to Friday's demonstration, Prime Minister Viorica Dancila said Iohannis was "inciting the population against the authorities", AFP reported. Sebastian Kurz, chancellor of Austria, which holds the European Union rotating presidency said: "We strongly condemn the violent clashes in Bucharest where numerous demonstrators and journalists were injured. We expect full explanations", he said on Twitter.