Hundreds of migrants are in a stand-off with police for a second night outside a Budapest railway station.
Earlier, scuffles broke out between the two sides as frustration among migrants boiled over outside Keleti station.
Many of the migrants have tickets and are insisting they be allowed to travel on to Germany and other countries, but Hungary says it is enforcing EU rules.
Meanwhile, Germany, Italy and France have called for "fair distribution" of refugees throughout the EU.
In a joint declaration, the countries' foreign ministers also called for Europe's asylum laws to be revised, the Italian foreign ministry said in a statement (in Italian).
With tens of thousands of migrants from the Middle East and Africa on the move through Europe, the EU's member states are struggling to agree a common policy for dealing with the crisis.
Italy and Greece have complained that they are overwhelmed by the numbers arriving on their shores. And while countries such as Germany are prepared to accept large numbers of asylum seekers, others, such as the UK, are not.
The BBC's Chris Morris in Brussels says the European Commission, the executive of the EU, is trying to draw up a list of safe countries of origin that failed asylum applicants can be sent back to.
And an EC spokeswoman has now said it is preparing proposals for a mechanism to automatically redistribute a proportion of those seeking asylum among EU states.
In other developments:
- Five children were among 12 migrants who drowned in Turkish waters while trying to reach Greece, officials said; images of a child's body washed up near the resort of Bodrum were circulating widely on social media
- Aid agency Medecins Sans Frontieres tweets that two of its boats have rescued nearly 1,000 people from the Mediterranean
- Police in Austria released 24 Afghan migrants who were in danger of suffocating from the back of a van
- A man was arrested in the German town of Massow after attacking people in a migrants' centre with pepper spray
- About 300 supporters of Hungary's right-wing nationalist Jobbik party waved flags and shouted abuse at migrants crossing the border from Serbia
- Eurostar trains between London and Paris were disrupted overnight after migrants got on to train tracks
The migrants camped overnight at Keleti station had been prevented from boarding trains on Tuesday.
They had bought tickets after Hungary appeared to abandon efforts on Monday to register migrants, allowing huge numbers to board trains to Vienna and southern Germany.
Hundreds of migrants again protested on Wednesday, chanting "Freedom, freedom" and waving train tickets.
Journalists at the scene said tensions were high with migrants involved in a stand-off with riot police.
A confrontation also broke out an another railway station in Budapest where a group of migrants occupied a platform after refusing to board a train sending them to a reception centre in the eastern city of Debrecen.
Police quoted by Hungarian TV said the "illegal immigrants" held their children aloft and demanded they be allowed to proceed freely to Germany.
Prime Minister Viktor Orban is due to meet EU chiefs on Thursday to discuss Hungary's handling of the crisis.
At-the-scene: Nick Thorpe in Budapest, Hungary
The stalemate around Keleti station continues. Many families are trying to decide what to do now. Everyone is asking each other the same question - will they be allowed to carry on their journeys or are they stuck here until their money runs out?
Lines of police are currently blocking the entrance to the station. People are very frustrated and very angry.
I was talking to two Syrian girls who said they hadn't washed for days. They said the Hungarians looked down on them, and that hotels and restaurants around the station were increasingly not allowing them in. They feel very humiliated by the situation.
Under an EU rule known as the Dublin Regulation, refugees should seek asylum in the first EU country they enter.
But this has proved hard to uphold, with border countries such as Hungary, Italy and Greece saying they cannot cope with the numbers. All three are members of the borderless Schengen Area.
In another development, spot checks on the border between Italy and Austria have been intensified following a request from Germany, Italian officials said.
The northern province of Bolzano said the German state of Bavaria had asked for "logistical support".
Bavaria, particularly the city of Munich, has seen record numbers of migrants arriving from the south. Austria is also performing spot checks on its border with Hungary.
The German government has already said it will allow Syrians arriving from other EU states to apply for asylum. But on Tuesday, a spokesman said the Dublin Regulation had not been suspended.
German Chancellor Angela Merkel has called for asylum seekers to be distributed more equally across the EU.
But on Wednesday, UK Prime Minister David Cameron said that taking "more and more" refugees was not the answer.
Greece saw the arrival of 23,000 migrants last week alone, said the EU's border control agency Frontex - an increase of 50% on the previous week.
Many arrive on the island of Lesbos, where, according to the Kathimerini newspaper, 17,500 migrants were registered in the last week.
Some 4,200 migrants were brought from Lesbos to the port of Pireaus, near Athens, early on Wednesday.
Greece's government says it lacks the resources to look after so many arrivals, but aid groups say the authorities should be doing more.
Migrants or refugees?
The word migrant is defined in the Oxford English Dictionary as "one who moves, either temporarily or permanently, from one place, area, or country of residence to another".
A refugee is, according to the 1951 Refugee Convention, any person who "owing to a well-founded fear" of persecution is outside their country of nationality and "unable" or "unwilling" to seek the protection of that country. To gain the status, one has to go through the legal process of claiming asylum.
The word migrant has traditionally been considered a neutral term, but some criticise the BBC and other media for using a word they say implies something voluntary, and should not be applied to people fleeing danger.
The number of migrants entering Europe has reached record levels, with 107,500 arriving in July alone.
Germany expects to take in 800,000 migrants this year - four times last year's total.
The risks for those travelling through Europe were highlighted last week by the deaths of 71 people found in a lorry that had travelled to Austria from Budapest.
EU interior and justice ministers will meet in Brussels on 14 September to address the crisis.