Bucharest — Protesters rallied on Saturday as Romania's ruling Social Democracy party began a congress amid criticism of the government and the party chairperson's leadership.

Dozens of demonstrators — as well as hundreds of supporters — gathered outside the building where the congress was taking place in the Romanian capital, where some 4 000 party members will elect 16 deputy presidents and a deputy leader at the meeting.

Supporters watched the congress which was broadcast on a screen while protesters yelled "You thieves!" and called the Social Democrats "The red plague." Police detained three people for disturbing public order.

Chairperson Liviu Dragnea initially planned to seek a vote of support at the congress, but withdrew that option as some party members claimed he arbitrarily changed party rules.

Dragnea can't be prime minister due to a 2016 conviction for vote rigging. Prosecutors launched a separate probe, charging him with embezzling European Union funds.

He denies wrongdoing.

The left-wing party retains its traditional support, but has been criticised after appointing three prime ministers in one year, and also for a tax overhaul which saw social security taxes shifted from the employer to the employee.