A pregnant woman was seen being stretchered from the scene and footage later emerged of distressed and injured children who had been in the line of fire when police used tear gas and water cannon.

Some 1,500 refugees who had been hoping to travel through Hungary are now blocked by a 3.5m-high fence.

Tensions spilled over at about 3pm when some refugees responded to the police tactics by throwing rocks and house bricks.
The majority ran desperately from the scene.

Sky News' Colin Brazier, reporting from the Roszke-Horgos border crossing, said tempers had been flaring for several hours, with refugees left at the fence without food, water and information.

"It's very fractious," reported Brazier. "There are young men who are really angry. It's a determined hard core of maybe a score - and behind them children and mothers.

"The imagery of this is being beamed around the world - people are going to look at this in other European capitals and be concerned."

Serbia sent ambulances to the crossing, where thick smoke billowed after the clashes.

The country reacted furiously to Hungary's tactics.

"This is being thrown across the border line, which no state has the right to do and because of that I protest in the strongest terms," Serbian minister Aleksandar Vulin said.

Serbia later said it would send extra police to the crossing to "prevent further attacks on the Hungarian police from our territory and in a humane and respectful way distance the refugeesfrom the fence and the Hungarian police".

Hungary had demanded more action from its neighbour, saying 20 officers had been injured in the clashes.

It also confirmed two children had been injured while being thrown over the fence - but said nothing of those filmed with either pepper spray or tear gas in their eyes.

Prior to the outbreak of violence at the 110-mile fence this afternoon, police had detained 519 people who had tried to get through.

The authorities have launched criminal proceedings against 46 people for allegedly crossing the border illegally.

Many refugee sare now crossing into Croatia in an attempt to avoid Hungary - but there are fears they could set off landmines left over from the Balkans War.

Demining experts have been sent to a border area where hundreds of refugees began crossing from Serbia on Wednesday.

"We have passed too much to give up now," said 43-year-old Mehmed from Damascus, holding his three-year-old daughter after crossing the border north into Macedonia from Greece.

"If not Hungary, we will have to find another way. Most probably Croatia and from there we will see."

Croatian Prime Minister Zoran Milanovic said his country was ready to accept refugees"regardless of their religion and the colour of their skin" and will help them pass through to Germany, Scandinavia or wherever else they want to go in Europe.

The divisions across Europe were reflected in comments by Romania's Prime Minister Victor Ponta, who said Hungary's actions evoked the continent's darkest era.

"Fences, dogs, cops and guns, this looks like Europe in the 1930s," he said. "And did we solve the refugee problem with this? No, we didn't.

"Erecting a fence only throws the problem into Serbia, into Croatia, into Romania."

Hungary has revealed it plans to extend its fence along parts of its border with Croatia and towards Romania - prompting Romania to summon the Hungary ambassador.

The human rights body Council of Europe has asked Hungary to explain legislation it adopted last week to deal with the refugee crisis.

Elsewhere, Slovenia has said it will temporarily establish controls on its border with Hungary in the face of the biggest movement in people since the Second World War. Austria has done the same.

EU interior and justice ministers will hold another crisis meeting next week after failing to agree a quota plan to redistribute 120,000 refugees across the continent.

Hungary, Slovakia and the Czech Republic are among the states opposed to the idea.

Meanwhile, Russia has proposed military-to-military talks with the United States on Syria, US Secretary of State John Kerry has said.