Hundreds of asylum seekers have poured into Budapest's international train station after police reopened it following a two-day standoff, but authorities cancelled all trains to western Europe, triggering chaos and confusion.

The main entrance was reopened around 8:15am (local time) and asylum seekers burst in, rushing towards a standing train on one of the platforms.

With the police seemingly absent, hundreds tried to get on the train, pushing, shoving and fighting with each other to board in the belief they were being allowed to continue their journey west to Austria, Germany and beyond.

Key points: No trains leaving for western Europe for "indefinite period"

No trains leaving for western Europe for "indefinite period" Police withdrawal coincided with parliamentary debate on migration laws

Police withdrawal coincided with parliamentary debate on migration laws Around 50,000 asylum seekers arrived in Hungary in August alone

A public announcement said, however, that no trains for western Europe would be leaving the Keleti station "for an indefinite period".

"In the interests of rail travel security, the company has decided that until further notice, direct train services from Budapest to western Europe will not be in service," Hungarian Railways said in a statement.

Shortly afterwards a train carrying between 200 and 300 asylum seekers left the station and headed toward the Austrian border.

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The train was stopped at the town of Bicske, where Hungary has a asylum seeker reception centre.

The asylum seekers banged on the train windows from the outside shouting "no camp, no camp". About 50 riot police were lined up near the train.

Police took the asylum seekers off and directed them onto buses to take them to the nearby camp, MTI reported, but there was resistance and police were forced to let them back on the train.

"There's a German flag on this train so we thought it went to Germany. So it's not going to Germany?" a man clinging with one hand to the doors of a train told a Reuters journalist, declining to be named.

The earlier standoff had become the latest symbol of Europe's migration crisis, the continent's worst since the Yugoslav wars of the 1990s.

The police withdrawal at the station coincided with the start of a special parliamentary session to debate tightening migration laws and punishment for those caught trying to breach a 3.5-metre-high fence Hungary is building on its border with Serbia.

Senior ruling party lawmaker Gergely Gulyas said the amendments could be passed this week and cut the number of illegal border crossings to "zero" by mid-September.

Earlier today pictures of a toddler's lifeless body washed up on a Turkish beach sparked horror around the world piling more pressure on European leaders who are facing the continent's biggest humanitarian crisis since the end of World War II.

The images of a tiny child lying face down in the surf at one of Turkey's main tourist resorts have been printed on the front pages newspapers all over Europe, putting a human face on the dangers faced by tens of thousands of desperate people who risk life and limb to seek a new life in Europe.

The boy, wearing a red t-shirt and blue shorts, has been identified as three-year-old Aylan Kurdi from Kobani, a war-torn Kurdish town on the Turkey-Syria border.

Hungary is a key arrival point for tens of thousands of asylum seekers entering the European Union, with some 50,000 entering the country in August alone.

On Monday, Hungary allowed several thousand to board trains bound for Austria and Germany, but the following day Keleti station was closed to anyone without an EU passport or a valid visa.

The move left around 2,000 men, women and children stranded around the station or in the underground transit zone, a makeshift refugee camp beneath the station where thousands have been sheltering on blankets in cramped conditions, looked after only by Hungarian volunteers.

Over the past two days there have been a number of demonstrations by several hundred of the asylum seekers chanting "Germany! Germany!" and tense standoffs with riot police as well as a number of scuffles.

"Normal people, abnormal people, educated, uneducated, doctors, engineers, any people, we're staying here. Until we go by train to Germany," said Mohamed, a Syrian protesting at the station.

Hungary a 'frontline' state in the crisis

Hungarian government spokesman Zoltan Kovacs defended his country's treatment of the asylum seekers.

"There is only one way to resolve this and this is by law, and re-establishing law and order," he told ABC's The World program.

"Not only at the railway station, but also at the borders of the European Union.

"These people we are facing and seeing at the railway station shouldn't be there.

Sorry, this video has expired Hungarian government spokesperson Zoltan Kovacs discusses the situation in Budapest.

"We have 2,000 to 3,000 illegal migrants arriving to Hungary daily, and obviously they have one thing in mind — to reach western Europe."

Hungary has in recent months joined Italy and Greece as a frontline state in Europe's migrant crisis.

The government of right-wing prime minister Viktor Orban has responded by erecting the controversial razor-wire barrier along its 175-kilometre border with Serbia.

In addition, parliament was due to begin debating a series of new laws to deal with the influx, including greater police powers and using the army at the border.

However Hungary's razor-wire barrier is proving ineffective in keeping out the tens of thousands of people trekking up from Greece through the western Balkans, with Hungarian authorities saying 2,284 crossed on Tuesday including 353 children.

Reuters/AFP