A group of protesters tried to break into the government building in Bucharest, but were held back by the police security cordon.
The protests were organized 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. Others threw bottles and rocks at riot police, who called the groups "provocateurs".
Thousands of Romanians took to the streets in the capital Bucharest as well as in other cities for a second day of protests, after on Friday, 450 people were wounded in confrontations with police.
The Guardian: Hundreds injured in Romania protests as emigrants return to fight corruption - "As the protest continued well into the night, riot police used a water cannon and increasingly sprayed tear gas into the crowd".
Video footage posted on social media show police beating some nonviolent protesters holding their hands up.
Over 400 people received medical care at the square that night and two gendarmes were attacked, it said.
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.
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". Messages projected on buildings around the square said "We are the people" and "No violence".
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 $5bn (£3.9bn) to one of the EU's least developed countries. They sent home just under $5 billion a year ago, a lifeline for rural communities in 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.
Mr Ostafi said: "I left to give my children a better life, which was not possible here then".
They say the governing leftist Social Democratic Party has proposed decriminalizing several corruption offences and has attempted to weaken the judiciary.
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. Those changes made it through parliament but are now being challenged in the country's constitutional court.
Some politicians from the ruling coalition derided the rally, saying they did not understand why the diaspora would protest. Here, police hold a protest outside government headquarters in the capital Bucharest.