Amnesty International has accused Balkan countries of mistreating migrants passing through their territories on the way to the European Union, saying people fleeing war are being "shamefully let down."
"Thousands of refugees, asylum seekers, and migrants -- including children -- making dangerous journeys across the Balkans are suffering violent abuse and extortion at the hands of the authorities and criminal gangs," the rights group said in a report.
Migrants fleeing war, poverty, and persecution are being "shamefully let down by a failing EU asylum and migration system which leaves them trapped without protection in Serbia and Macedonia," the London-based group said.
"As increasing numbers of vulnerable refugees, asylum-seekers, and migrants become trapped in a Balkan no-man's land, the pressures on Serbia and Macedonia are mounting," said Gauri van Gulik, Amnesty's deputy director for Europe and Central Asia.
He called the Balkan countries "a sink for the overflow of refugees and migrants that nobody in the EU seems willing to receive."
Many migrants told the rights group that they have been forced to pay bribes of up to 100 euros to police while passing through the Balkans.
Last month, Serbian police arrested 29 police officers and nine customs officials suspected of corruption and abuse of power, accusing them of taking bribes to let migrants illegally pass through the border to Hungary.
But even with such efforts, "Serbia and Macedonia have to do much more to respect migrants and refugees' rights," van Gulik said.
Still, "it is impossible to separate the human rights violations there from the broader pressures of the flow of migrants and refugees into and through the EU, and a failed EU migration system."
The number of migrants and refugees from Syria, Afghanistan, Egypt, Eritrea, Iraq, Nigeria, Somalia, Sudan, and Tunisia, traveling overland through the Balkans on their way to EU, has dramatically increased in recent years.
The number of people apprehended crossing the Serbia-Hungary border alone has risen by more than 2,500 percent since 2010 -- from 2,370 to 60,602, Amnesty said.
The journey takes them by sea from Turkey to Greece and then overland across Macedonia and Serbia towards EU-member Hungary, a route that is increasingly used as it is considered less deadly than sailing across the Mediterranean from Libya.
More than 1,800 people have been killed attempting to cross the Mediterranean this year alone, according to the United Nations.
The growing popularity of the Balkan route prompted Hungary's parliament recently to pass legislation tightening asylum rules and authorizing the building of a fence along the country's southern border with Serbia to stem the flow of illegal migrants.
Amnesty's report is based on four research missions to Serbia, Hungary, Greece, and Macedonia between July 2014 and March 2015, and interviews with more than 100 refugees and migrants.
Migrants reported being pushed, slapped, kicked, and beaten by Serbian police near the border with Hungary, and an Afghan refugee told Amnesty that "a woman who is five months pregnant was beaten."
Many migrants were reported to have been "arbitrarily detained by the authorities" for prolonged periods, without any legal safeguards or the opportunity to claim asylum.
In addition, refugees and migrants are also vulnerable to financial exploitation by smugglers and attacks by criminal groups, the report said.
Successful asylum applications in Serbia and Macedonia are very rare, with only one person granted refugee status in Serbia in 2014 and 10 in Macedonia, according to Amnesty.
Discouraged by the slow progress in processing their applications, most asylum seekers continue their journey into Hungary where they face further rights violations, Amnesty said.
"Those detected entering Hungary irregularly are routinely detained, often in overcrowded and degrading conditions, or ill-treated by police officers," according to the report.
Amnesty called for "a much broader rethink of EU migration and asylum policies."