BUCHAREST, ROMANIA, JUNE 18 -- The lower house of Romania's legislature voted overwhelmingly today to empower the Interior Ministry to remove anti-government demonstrators who defiantly blocked traffic for a second day in front of Bucharest University.

Undeterred by the vote, hundreds of demonstrators milled about, shouting anti-government slogans, but no police or soldiers could be seen. By midnight, the demonstrators had dwindled to fewer than 50, and traffic was again flowing freely.

Late tonight, Romanian television said authorities had arrested three opposition leaders on charges connected with the protests here last week, including student leader Marian Munteanu, who students said had been transferred from a state hospital to an Interior Ministry clinic.

Munteanu suffered a fractured skull and a broken arm and leg at the hands of club-wielding government supporters Thursday, student activists said. Others arrested today were leading opposition activists Dumitru Dinca and Nica Leon, state television said.

The government's decision to ask for formal legislative approval apparently reflected increasing official realization that the two-day rampage against demonstrators last week by 10,000 coal miners called out by the government had seriously damaged Romania's image abroad, especially in the West. Opposition legislators noted that the government took no such precautions before summoning the miners last week to put down the protests.

Amid U.S. expressions of displeasure, American Ambassador Alan Green Jr. cut short consultations in Washington and returned here to warn: "It is clear that the democratic process in Romania has come to a stop."

In an effort to improve its image abroad, the government made sure that the leading opposition newspaper, Romania Libera, would appear Tuesday after a four-day hiatus caused by intimidation from printers and the miners. Staffers voted 70 to 19 to renew publishing after printers reversed their position and urged them during a four-hour meeting to brave the miners' threats of retaliation.

The reopening of newspapers and magazines closed last week was one of the four points that Green said Washington considered essential to "get progress toward democracy back underway."

On Saturday, the government issued a statement that appeared to answer two other U.S. demands to "publicly guarantee the safety of people to exercise their legitimate rights of freedom of expression and democratic dissent," and "to engage in constructive dialogue with democratic opposition parties and other groups."

Both legislative houses today moved to set up a joint commission to investigate last week's three days of disorder. The turmoil began when police ended a 53-day sit-in by anti-government activists at what they called their "communist-free zone," which was occupied by demonstrators again Sunday night and today.

But the government has shown no disposition to meet the remaining U.S. demand to "publicly pledge that vigilantes," as Green's statement describes the rampaging miners, "will not be encouraged or allowed."

The only slight step in that direction was a Bucharest radio statement today that the government has rejected an offer by mine leader Miron Cozma to bring his men back to Bucharest. The radio said he offered their services after watching television coverage of anti-government demonstrators near the university Sunday night.

Green said President Bush and Secretary of State James A. Baker III instructed him to "convey to the Romanian government the very serious concern of the United States about violence that occurred in Bucharest June 14 and 15, 1990, and the resulting damage to Romania's progress toward democracy."

Speaking at the democratic-reformist Group for Social Dialogue, Green denounced the "vigilante actions inspired by President {Ion} Iliescu and the Romanian government last Thursday and Friday."

"Frankly, I'm shocked by what I've seen and heard," he said after visits to leaders and devastated party offices of the opposition Peasants and National Liberal parties.

The vote empowering Interior Minister Doru Ursu to intervene against the demonstrators was adopted by 301 of the lower house's 397 members, with 72 votes against and 7 abstentions.

Earlier, as both houses discussed setting up a joint commission to investigate the turmoil, Radu Campeanu, the National Liberal leader, insisted that it have the right to "investigate the investigators." The remark was taken to mean that he believes any such commission would be dominated by the pro-government National Salvation Front.