Around a hundred migrants and asylum seekers braved scorching heat on Saturday to continue a march toward Serbia's border with Hungary meant to draw attention to the plight of thousands of people facing closed borders after fleeing war and poverty. Some wore towels on their heads to ward off the sun as they slowly moved, stopping occasionally to rest in the shade along the road leading north toward the European Union. Their feet bruised from walking, dozens have given up and stayed behind. Some 300 young men and boys set off on Friday from Belgrade toward the Hungarian border 200 kilometers (120 miles) away, to protest its decision to keep the border closed for most of the asylum seekers, which has left a few thousand stranded in Serbia. Hungary has recently strengthened anti-migrant controls on its southern border with Serbia, admitting about 30 people a day, mostly families with small children, and pushing back those caught trying to cross illegally. Hundreds of migrants have been staying in make-shift camps along the border with almost no facilities. Some of those marching to Hungary wore T-shirts reading: "Stop the war if you want to stop refugees," or "Open borders." Most said they were from Afghanistan and Pakistan, and stand little chance of crossing the Hungarian border into the European Union. Some said they will stage a hunger strike once they arrive at the border. "We want to be in the limelight so we could deliver the messages to the global leaders what is happening with the refugees," said Roohul Amin Afridi, 33, from Afghanistan. Faced with a pileup of refugees, Serbian authorities also have announced stricter joint army and police border controls with Bulgaria and Macedonia, where migrants mostly enter Serbia. Most of the people stranded in Serbia have refused to apply for asylum there, fearing it would ruin their chances of one day reaching any EU nation. International medical aid agency Doctors Without Borders on Friday warned of a "sharp increase" in violence against migrants and refugees since the Balkan borders were closed in March.