police were injured. 6 April: Migrants protested at the Port of Piraeus in Greece when authorities tried to move them from a makeshift camp to official migrant shelters. One migrant threatened to throw a baby at police after they tried to stop him from smashing a car. 10 April: Clashes erupted at the Idomeni migrant camp on the Greece-Macedonia border. Hundreds of migrants attempted to break through the border barrier and threw stones at Macedonian police. Police responded by firing tear gas, stun grenades and plastic bullets. More than 200 migrants and at least 15 police officers were injured. A Greek government spokesman called the Macedonian police actions "dangerous and deplorable". 12 April: Austria began building a fence and registration center at the Brenner Pass on the Italian border. Austria's Defense Minister threatened to shut the Brenner Pass unless Italy stemmed the northward flow of migrants. The EU and refugee agencies criticized the measures. 15 April: There were clashes between a vigilante group and hundreds of migrants at a makeshift migrant camp outside Stalingrad metro station, Paris. Police used tear gas to disperse the crowds, and four people were taken to hospital. 16 April: Pope Francis took 12 Syrian refugees back with him to Vatican City after visiting a camp on the Greek island of Lesbos. The three families, including six children, are all Muslim and had their homes bombed during the Syrian civil war. The Vatican stated that Pope Francis wanted to "make a gesture of welcome" to refugees. 18 April: The Turkish government threatened to withdraw from its agreement with the EU unless the EU grants visa-free travel for Turkish citizens by June. Withdrawing from the agreement would mean that Turkey would no longer take back migrants from the EU. 18 April: Migrants pelted Greek police with stones at Idomeni migrant camp after a migrant was hit by a police van. Police fired tear gas to break up the crowds. 19 April: Adverts by the organization 'Refugees Welcome' began being shown to German YouTube users when they search for anti-mass immigration videos. The adverts cannot be skipped and use YouTube's advertising system to target certain search terms. 20 April: The Swiss government said it had drawn up plans to deploy 2,000 soldiers at border crossings should there be a major inflow of migrants to the country. 24 April: Austrian Freedom Party candidate Norbert Hofer, campaigning against mass immigration,