Some chanted "This is Serbia" while other carried banners appealing for help from Russia, which has opposed Kosovo's independence.
On Sunday, Kosovo's majority ethnic Albanians celebrated with fireworks late into the night after parliament's declaration.
In Brussels the chairman of the EU meeting, Slovenian Foreign Minister Dimitrij Rupel, said he understood "many of the member states will recognise" Kosovo.
His British and French colleagues insisted Kosovo was a unique case and called for EU unity on the issue, the BBC's Oana Lungescu reports.
| I understand many EU members will recognise Kosovo Dimitrij Rupel Slovenian Foreign Minister |
UK Foreign Secretary David Miliband described Kosovo as a "unique situation which deserves a unique response".
"I think it's very important that we recognise that all of the countries of the Western Balkans are European countries and therefore it's critical that Europe shows real leadership in how it ensures that peace and stability are the order of the day," he said.
But Spanish Foreign Minister Miguel Angel Moratinos said Spain would not recognise Sunday's declaration because it "does not respect international law".
German Chancellor Angela Merkel said her country, which has been predicted to back Kosovo independence, would not declare its position on Monday.
"The aim is to have a platform of unity within the EU, on which each member state can act," she said.
The EU has already agreed to send about 2,000 police, justice and civil administration officials to oversee Kosovo and help develop the province's institutions.
Russian opposition
A split emerged at the UN Security Council on Sunday when Russia said Kosovo's declaration should be null and void.
| KOSOVO PROFILE Population about two million Majority ethnic Albanian; 10% Serb Under UN control since Nato drove out Serb forces in 1999 2,000-strong EU staff to take over from UN after independence Nato to stay to provide security |
Russia's UN ambassador said there was no basis for changing a 1999 security council resolution on Kosovo's status - which hands Kosovo to the UN.
But seven Western states including the United States, the UK, Belgium and France issued a statement saying the situation had moved on.
Russia has indicated that Western recognition of an independent Kosovo could have implications for the breakaway regions of Abkhazia and South Ossetia in Georgia.
China expressed its "deep concern" about Kosovo's declaration, urging it to reopen talks with Serbia.
UN Secretary General Ban Ki-moon called on all sides to keep to their commitments and refrain from violence.
A second emergency session is due to be held later on Monday. Unfortunately today Kosovo and Serbia are to become two dispensable chess-pieces of EU/NATO and Russia Mat, Ljubljana, Slovenia
The independence declaration said Kosovo would be built in accordance with the UN plan drawn up by former Finnish President Martti Ahtisaari.
The international military and civilian presence - also envisaged by the Ahtisaari plan - was welcome, Kosovo's Prime Minister Hashim Thaci said.
There should be no fear of discrimination in new Kosovo, he said, vowing to eradicate any such practices.
Violence
A hand grenade thrown at a UN court building in the flashpoint town of Mitrovica caused slight damage but otherwise there were no reports of trouble in Kosovo.
In Belgrade, clashes between gangs of youths and riot police went on into the early hours of Monday morning.
Demonstrators broke windows at the US embassy and also attacked the Serbian government building and the embassy of Slovenia which currently holds the EU presidency.
The Serbian government has called for a mass protest rally against the Kosovo declaration later in the week.
Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/europe/7249909.stm
Any thoughts on the new Kosovar independence? I am usually in favor of self-determination movements, and in general am all for Kosovo as an independent state. Still, the debate in the EU is interesting and brings up a lot of questions about when and for whom self-determination is fair and appropriate. And this is hard, because by what criteria is the right to self determination decided? These are major questions in the EU, especially since Spain, France, and a handful of other states have significant separatist movements. Is it inconsistent to say that Kosovo can be independent but the Basque region has to remain part of Spain or Corsica has to remain part of France? The problem is that it is really not possible to continually split nations into tinier and tinier entities; they are not economically or politically viable (at some point). If I have to put forth a general statement I would suggest that ethnic enclaves or minority regions should be given significant autonomy (as in Spain) if they exist in liberal democratic states where their rights are protected. If, on the other hand, they exist in an autocratic state where they face abuse or persecution then the international community should support their independence. I could go on and be more detailed, but this is getting long.