The EU has urged all sides in Moldova to stay calm and refrain from violence
Romania has condemned as "arbitrary and discriminatory" new measures brought against Romanian nationals in Moldova, following Tuesday's violent protests.
Moldova and Russia have accused Romania of fomenting the unrest and even attempting to inspire a coup.
Moldova reacted by imposing a visa regime on Romanians, expelling Romania's ambassador and denied entry to Romanian and other journalists.
Romania said the visa scheme was "reckless" and broke a Moldova-EU pact.
Romanian Foreign Minister Christian Diaconescu added that the EU had not been informed of the move.
"While understanding the complexity of Moldovan-Romanian relations, we call on the government of Moldova to resume normal relations with Romania," leading EU foreign ministers said in a statement.
Thousands of young people stormed the parliament in Chisinau on Tuesday in protest at Sunday's election result, which was a landslide for the ruling Communist Party.
Some of the demonstrators reportedly shouted "We are Romanians!" and brandished Romanian flags.
Russia's Foreign Minister Sergei Lavrov called on the EU to intervene.
"We hope that the EU and the Romanian leadership, which publicly condemned the violence, will take action to ensure that Romanian flags and Romanian slogans are not used as the cover for undermining Moldovan statehood," he told Russia's RIA Novosti news agency.
The BBC's Rupert Wingfield-Hayes says that what Mr Lavrov means is the protests were an attempted coup by those who want Moldova to unite with neighbouring Romania.
Most of those who witnessed Tuesday's riots in the capital, Chisinau, say they were spontaneous and disorganised, but Russia appears to believe they are far more sinister, our correspondent says.
Russia has watched old allies in Ukraine and Georgia thrown out and replaced by pro-Western governments deeply unsympathetic to Moscow, and now it fears the same thing could be about to happen in Europe's poorest country, he adds.
Brussels has also sent an envoy to Moldova to mediate in the dispute between President Vladimir Voronin's ruling Communist Party and the three centre-right opposition parties over the result of Sunday's general election.
Although OSCE observers concluded the vote was generally fair, opposition parties and many students have accused the authorities of fraud.
They have called for ballots to be recounted or the vote to be re-held - a request rejected so far by the government.