Militaru said officers were ordered by Bucharest officials to evacuate Victory Square late Friday after an hours-long protest in front of government offices that drew tens of thousands demanding the government's resignation.
Many demonstrators needed treatment after inhaling pepper spray and tear gas, while others suffered blows, hospital sources said.
This summer, the PSD also moved forward with a judicial overhaul that some observers see as a threat to the rule of law in Romania.
"My children work in Spain and they would like to come back".
Protest organisers demanded the government resign over recent legislation and measures that they say are tailor-made to advance the interests of corrupt politicians.
Friday's protests were organised and promoted by groups of Romanians working overseas, angry at what they say is entrenched corruption, low wages and attempts by the PSD to weaken the judiciary in one of the European Union's most corrupt states.
People shine the lights of their mobile phones during a protest outside the government headquarters, in Bucharest, Romania, Saturday, Aug. 11, 2018.
Austrian Chancellor Sebastian Kurz, whose country now holds the European Union rotating presidency, criticised the violence, which also saw a cameraman for Austria's public broadcaster hurt. "We expect full explanations".
"Freedom of expression and, related to that, freedom of the press are basic freedoms of the European Union, which we clearly recognise and which must be unconditionally protected".
There were accusations that soccer hooligans had infiltrated the largely peaceful protest and deliberately committed acts of violence.
"Have no fear! Romanians will rise up!" and "You thieves!" they yelled.
Some protesters threw water bottles at riot police during the protest in Bucharest. Hundreds of people â some carrying Romanian flags â started gathering around a central square in Bucharest for a second day of protest, with the crowd expected to grow as the evening progresses.
Another demonstrator, Madalina, 22, said of Friday's clashes: "We couldn't breathe and we had to seek shelter in the surrounding streets".
In a statement issued Friday night, Romania's President Klaus Iohannis condemned the "brutal intervention of the Gendarmerie", saying their actions were "strongly disproportionate with the demonstrations of the majority of people in Victoria Square".
Prime Minister Viorica Dancila, in turn, accused Iohannis of "inciting the population against the authorities" and "using the dramatic effects of the events".
But in July, Laura Codruta Kovesi, the leading anti-corruption prosecutor, was fired.
Critics say Romania has lost ground in fighting corruption since the ruling Social Democratic Party assumed power in 2016.
In early 2017, Romanian protesters took to the streets in response to a decree that loosened corruption laws.