BUDAPEST (Reuters) - Hungary started building a fence on Monday along its border with Serbia to try to stop illegal migrants entering from the south, a barrier which German Chancellor Angela Merkel has said makes "no sense".
Tens of thousands of migrants, mainly from the Middle East and Africa, use the Balkans route to get into the European Union, passing from Greece to Macedonia and Serbia and then to the EU's visa-free Schengen zone that starts in Hungary.
Work on the 4-meter (12 feet) high and 175-km (110 mile) long fence started near Morahalom, a town 180 km southeast of the capital, Budapest, state television channel M1 said.
Hungary has registered more than 70,000 migrants so far this year, compared with 43,000 in the whole of last year.
Most migrants travel on to wealthier parts of the EU, but Hungary's government has said those states might send illegal migrants back to Hungary. It blocked just such a move last month, provoking tensions with Vienna.
Although the EU's rules allow countries to send migrants back to their first point of entry into the bloc, there is no evidence of a large scale of such returns to Hungary yet.
Shelters in Hungary and Austria are overcrowded and late last month Hungarian police used tear gas to subdue hundreds of migrants fighting each other and throwing rocks in a camp in the eastern city Debrecen.
The United Nations and the Council of Europe have criticized changes to Hungary's asylum laws, saying they would harm asylum-seekers' right to seek safety there and put them at risk.
(Reporting by Sandor Peto; Editing by Louise Ireland)