Wounded people walk after clashes with riot police in central Kiev February 18, 2014. Ukrainian riot police advanced on the heart of 12-week-old protests against President Viktor Yanukovich on Tuesday and security forces set a deadline to end disturbances after at least five protesters were reported killed in a day of clashes. (Photo by Vlad Sode/Reuters)

People gather at the site of a bomb explosion in Sanaa December 23, 2014. Five bombs exploded on Tuesday in Sanaa's old quarter, where many supporters of the Shi'ite Muslim Houthi group live, killing at least one person and wounding another, a Yemeni security official said. No one has claimed responsibility for the attacks, but the Houthis have been fighting the Sunni Islamist militant al Qaeda group and allied tribesmen since its gunmen captured Sanaa in September and forced the resignation of a government they had long seen as corrupt. (Photo by Khaled Abdullah/Reuters)

In this Wednesday, January 23, 2019, an anti-government protester covers her face with a Venezuelan flag, and uses toothpaste around her eyes to help lessen the effect of tear gas, during clashes with security forces after a rally demanding the resignation of President Nicolas Maduro in Caracas, Venezuela. The head of Venezuela's opposition-run congress declared himself interim president at the rally, until new elections can be called. (Photo by Fernando Llano/AP Photo)

An opposition activist clashes with the police during a march against Venezuelan President Nicolas Maduro held on May Day, in Caracas on May 1, 2017. Security forces in riot vans blocked off central Caracas Monday as Venezuela braced for pro- and anti- government May Day protests one month after a wave of deadly political unrest erupted. (Photo by Federico Parra/AFP Photo)

Chinese soldiers leave after Chinese President Xi Jinping inspected troops of People's Liberation Army (PLA) Hong Kong Garrison at the Shek Kong Barracks in Hong Kong, Friday, June 30, 2017. Xi landed in Hong Kong Thursday to mark the 20th anniversary of Beijing taking control of the former British colony, accompanied by a formidable layer of security as authorities showed little patience for pro-democracy protests. (Photo by Kin Cheung/AP Photo)

In this photo taken Thursday, January 16, 2020, a Samburu boy uses a wooden stick to try to swat a swarm of desert locusts filling the air, as he herds his camel near the village of Sissia, in Samburu county, Kenya. The most serious outbreak of desert locusts in 25 years is spreading across East Africa and posing an unprecedented threat to food security in some of the world's most vulnerable countries, authorities say, with unusual climate conditions partly to blame. (Photo by Patrick Ngugi/AP Photo)

Women holding the Singapore national flag pose for a photograph at the Merlion Park to mark the 55th National Day celebrations in Singapore on August 9, 2020. National Day is celebrated in commemoration of Singapore's independence from Malaysia in 1965. (Photo by Roslan Rahman/AFP Photo)

Race goers enjoying Grand National Day at the Randox Grand National Festival at Aintree, Liverpool, Britain, 09 April 2022. This year's Grand National is the 174th edition of the legendary annual horse race at the Aintree Racecourse in Liverpool. (Photo by Peter Powell/EPA/EFE)