A demonstrator holds a street sign to shield himself as he stands amidst a cloud of tear gas during a protest against the government of President Nicolas Maduro in Caracas, February 22, 2014. A female student and a young supermarket worker were the latest fatalities from Venezuela's political unrest as the death toll from 10 days of violence rose on Saturday to at least eight. REUTERS/Carlos Garcia Rawlins

Anti-government protesters stand with makeshift shields made from traffic signs next to a barricade in Kiev January 24, 2014. Ukrainian protesters erected more street barricades and occupied a government ministry building on Friday after the failure of crisis talks with President Viktor Yanukovich, pointing to a further hot weekend of protest. REUTERS/Valentyn Ogirenko

Riot police use a water cannon to disperse anti-government protesters near the Middle East Technical University (ODTU) in Ankara March 11, 2014. A 15-year-old Turkish boy who suffered a head injury during anti-government protests in Istanbul last June died on Tuesday after spending months in a coma, triggering renewed clashes between police and his family's supporters. Berkin Elvan, then aged 14, got caught up in street battles between police and protesters on June 16 after going out to buy bread for his family. He was struck in the head with a suspected police tear-gas canister and went into a coma. Elvan had become a rallying point for critics of Prime Minister Tayyip Erdogan's government and they held regular vigils at the hospital where he lay in intensive care. No police officer has been prosecuted in connection with the Elvan case. REUTERS/Umit Bektas

A Palestinian uses a sling to throw back a tear gas canister fired by Israeli troops during clashes in the West Bank city of Bethlehem October 14, 2015. Seven Israelis and 30 Palestinians, including children and assailants, have been killed in two weeks of bloodshed in Israel, Jerusalem and the occupied West Bank. The violence has been partly triggered by Palestinians' anger over what they see as increased Jewish encroachment on Jerusalem's Al-Aqsa mosque compound, also revered by Jews as the site of two destroyed Jewish temples. REUTERS/Mussa Qawasma - RTS4FK3

Protesters shield themselves from police water cannon during a May Day demonstration in Istanbul May 1, 2014. Turkish police fired water cannon and tear gas on Thursday to prevent hundreds of protesters from defying a ban on May Day rallies and reaching Istanbul's central Taksim Square, the focal point of weeks of protests last summer. REUTERS/Murad Sezer

Riot police scuffle with pro-democracy students after hundreds of protesters stormed into a restricted area at the government headquarters, after a rally ahead of the October 1 "Occupy Central" civil disobedience movement in Hong Kong September 27, 2014. Hong Kong riot police used pepper spray on Saturday to disperse dozens of students who had stormed government headquarters, but an equal number held their ground in protests against Beijing's tightening grip on the city. REUTERS/Tyrone Siu

A protestor uses a tennis racket to return a tear gas canister during a demonstration to protest the government's proposed labour law reforms in Nantes, France, June 2, 2016. REUTERS/Stephane Mahe TPX IMAGES OF THE DAY - RTX2FBII

CANADA - YEAREND PICYURES 2001 - A protestor hits a teargas canister back at riot police with a hockey stick on the second day of protests against the third Summit of the Americas, April 21, 2001. The heads of 34 Western Hemisphere nations are met to discuss the creation of a free trade zone. REUTERS/Bob Strong RR/HB/SV - RTRQGON