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)

Fire fighters, emergency service vehicles and a helicopter in Moskovsky Prospekt at the entrance to Tekhnologichesky Institut station of the St Petersburg metro in the aftermath of an explosion which occurred in a train at 14:40 Moscow timeon April 3, 2017. (Photo by Peter Kovalev/TASS)

Israeli police inspectors stand next to a bus damaged in an explosion March 23, 2011 in Jersalem, Israel. A bomb exploded near a crowded bus, wounding passengers in what appeared to be the first militant attack in the city in several years.

In this photo provided by The Daily Free Press and Kenshin Okubo, people react to an explosion at the 2013 Boston Marathon in Boston, Monday, April 15, 2013. (Photo by Kenshin Okubo/AP Photo/The Daily Free Press)

P.S. All pictures are presented in high resolution.

Lasha Pataraia pulls a truck, which weighs 8,250kg (8 tons), with his ear during an event to break the Guinness Book of World Records in Rustavi, outside Tbilisi November 29, 2012. The 32-year-old broke a Guinness record after he managed to pull the truck with his ear for 21,50 metres (70.5 feet), according to organisers. (Photo by Irakli Gedenidze/Reuters)

Women comfort each other as they mourn over the death of a family member who was killed in a bomb blast, at a local hospital in Lahore, Pakistan, Sunday, March, 27, 2016. A bomb blast in a park in the eastern Pakistani city of Lahore has killed tens of people and wounded scores, a health official said. (Photo by K.M. Chuadary/AP Photo)

An Iraqi woman grieves at the scene of a bomb attack in Jameela market in the Iraqi capital's crowded Sadr City neighborhood Baghdad, Iraq, Thursday, August 13, 2015. A massive truck bomb ripped through a popular Baghdad food market in a predominantly Shiite neighborhood in the early morning hours on Thursday, killing dozens of people, police officials said. (Photo by Karim Kadim/AP Photo)