More than 4,000 Bulgarians shouting "Democracy!" and "Glasnost!" rallied Friday outside the National Assembly in that country's first mass protest in four decades of Communist rule.
The cheering but orderly crowd had joined a brief march organized by an unofficial ecology group to present lawmakers with a petition on environmental problems.
"It was electrifying, the biggest sign of hope that seems to be mounting here," said one Western diplomat in the crowd.
Bulgaria is one of the most repressive and politically isolated nations in Eastern Europe. In contrast to sweeping democratic changes in Hungary and Poland, restructuring in Bulgaria has so far been limited to attempts to streamline a stagnating economy.
On Friday, uniformed police ringed the central Alexander Nevski Square but did not prevent six people among the crowd of demonstrators from approaching the National Assembly building to present the petition.
As the petition was handed over, the crowd cheered, sang parts of the national anthem and shouted for glasnost , the Russian word for openness that is a key part of Soviet leader Mikhail S. Gorbachev's reform program.
Responding to a request shouted by Petar Slabakov, secretary of the ecology group known as Eco-Glasnost, the crowd dispersed peacefully about 15 minutes later.
Eco-Glasnost spokeswoman Dimitrina Petrova said she had handed the petition with 11,545 signatures to Atanas P. Dimitrov, deputy president of the National Assembly. The petition protested plans for a hydroelectric plant.
"He said it seemed fine from the procedural point of view and would be considered," Petrova said.
The rally was also attended by foreign diplomats and delegates of 35 nations to an international conference on environmental protection that ended Friday. A number of leading political dissidents also took part.
Dissident activity in Bulgaria has flourished in the last three weeks, with activists using international interest in the conference to publicize their grievances. Eco-Glasnost and a number of political dissident groups have held their first public meetings and press conferences during this period.
On Thursday night, more than 500 Bulgarians packed a Sofia movie theater for the first public gathering of the Club for the Support of Perestroika and Glasnost. Speakers' appeals for freedom of speech and democratic reform were met with standing ovations.
Eco-Glasnost leaders and political dissidents at Friday's rally were cheered, hugged by onlookers and asked for autographs.
However, a number of activists and Western diplomats say they fear that Bulgarian authorities will resume their usual crackdown on reform once foreign delegations and journalists leave Sofia.
Bulgarian police beat and detained Eco-Glasnost members last week as they prepared to gather signatures for their petition. Authorities later said the incident was a misunderstanding.
Western delegations at the environmental meeting, organized by the Helsinki Conference on Security and Cooperation in Europe (CSCE), urged Bulgaria to encourage the activities of unofficial groups in line with the conference's pledges on human rights.