KHARKIV: A Ukrainian serviceman walks along defense structures near a front line in Kharkiv Region, on Monday, December 25 (REUTERS/Viacheslav Ratynskyi)

PIEDRAS NEGRAS: Irma Yolani Cruz, 31, carries her 11-year-old son and her 1-year-old daughter, Ariana, across the Rio Grande from Piedras Negras, Coahuila, Mexico, with her husband Jamie Ariel Rapalo, 32, and their other two sons, ages 4 and 8, after traveling for two months and 10 days, on Saturday, December 23 (REUTERS/Cheney Orr)

ISRAEL-GAZA BORDER: An Apache helicopter passes in front of the moon near the Israel-Gaza border, on Monday, December 25 (REUTERS/Amir Cohen)

SOUTHERN ISRAEL: An Israeli self-propelled artillery unit fires, seen from southern Israel, on Tuesday, December 26 (REUTERS/Violeta Santos Moura)

BELGRADE: Police officers cover the door of the city hall as a protester raises a stick during a protest by supporters of the opposition Serbia Against Violence (SPN), after the SPN alleged major election law violations in the Belgrade city and parliament races, in Belgrade, on Sunday, December 24 (REUTERS/Marko Djurica)

ATHENS: A person releases a sky lantern during Christmas festivities in Athens, on Sunday, December 24 (REUTERS/Louiza Vradi)

VALPARAISO: Sea lions congregate in front of a police car, obstructing the path of riot police, during clashes with fishermen in Valparaiso, on Thursday, December 28 (REUTERS/Rodrigo Garrido)

IBI: Revelers battle with flour and eggs during the traditional Els Enfarinats (The Floured) festival in Ibi, on Thursday, December 28 (REUTERS/Eva Manez)

RAFAH: People bury Palestinians who were killed by Israeli strikes and fire, after their bodies were released by Israel, at a mass grave in Rafah in the southern Gaza Strip, on Tuesday, December 26 (REUTERS/Ibraheem Abu Mustafa)

TOKYO: People wearing Santa Claus outfits pose for photos before handing out gifts and cleaning up the street in Tokyo, on Saturday, December 23 (REUTERS/Kim Kyung-Hoon)