( CNN ) -- Moldova 's president Wednesday accused Romania of involvement in a huge anti-communist protest , much of it coordinated on Facebook and Twitter , which saw government buildings ransacked and police arrest scores of demonstrators . Protests over Moldova 's election have gathered pace , fueled by Facebook and Twitter . Vladimir Voronin described riots in the Moldovan capital Chisinau against his ruling Communist party 's victory in Sunday elections as `` very serious '' and pledged to take action in response . `` Romania is involved in everything that has happened , '' he said , according to the RIA-Novosti news agency . `` Patience also has its limits . '' An estimated 10,000 mainly students gathered Tuesday to protest what they say was a rigged election . Many in the crowd were summoned using social networking tools , particularly Twitter . IReport : Send your photos and emails . Protesters threw bricks at riot police who responded with batons and water cannon . Outnumbered , police retreated , leaving rioters to enter the parliament building and presidential offices where they smashed windows and started fires . See images of the chaos » . Demonstrators claim Voronin 's ruling Communist Party manipulated Sunday 's election results to make it appear that it had won 50 percent of the vote , a majority that would allow the party to and amend the Constitution to allow Voronin to rule for a third term . Although election observers from the Organization for Security and Cooperation in Europe found the voting largely free , many in the former Soviet state disagreed . `` There were too many frauds , '' said Alina Radu , director of the weekly newspaper Ziarul de Garda . Her newspaper 's Web site asked readers Wednesday morning to send in instances of voter abuse . `` In just half an hour , we had tens and hundreds of cases , '' Radu said . Voronin said he was expelling the Romanian ambassador to Moldova and imposing visa restrictions on Romanians in response to the violence , RIA-Novosti said . The agency reported that Romania has denied involvement and was threatening retaliatory measures . Analysts saw Tuesday 's demonstrations as a student-led action that `` caught the opposition political leaders by surprise . '' `` Because I think that after talking to the Western observers , they did n't expect they would get any support for protests , '' said Tammy Lynch , senior fellow at Boston University 's Institute for the Study of Conflict , Ideology and Policy . `` It seemed to be undirected , '' Lynch said . `` A lot of students felt angry they were being ignored and took out their anger on buildings . '' Moldova 's ties with Romania have become increasingly strained under Voronin , who has steered his country diplomatically closer to Russia since taking power in 2005 . The president has repeatedly accused Romania of wanting to absorb his country . -- CNN 's Saeed Ahmed contributed to this report .
Up to 10,000 gathered Tuesday in Moldova 's capital Chisinau . Many demonstrators summoned by Facebook or Twitter . Protesters claim recent parliamentary elections were rigged .