By David Alire Garcia MEXICO CITY (Reuters) - A teenage student suffering from depression shot three students and a teacher at a private school in northern Mexico on Wednesday before killing himself in what state officials called an unprecedented attack that was caught on security video.

By Eduardo Simões SAO PAULO (Reuters) - Heavily armed police on Wednesday entered the prison where 26 inmates were butchered in recent days and separated members of rival drug gangs waging a turf war that set off a wave of riots in Brazil's overcrowded penitentiary system.

By Michelle Nichols UNITED NATIONS (Reuters) - The United Nations Security Council needs to push Iran to abide by an arms embargo, outgoing U.S. Ambassador Samantha Power said on Wednesday amid U.N. concerns that Tehran has supplied weapons and missiles to Lebanese Shi'ite group Hezbollah.

By Jeff Mason and Ayesha Rascoe WASHINGTON (Reuters) - President Barack Obama suggested on Wednesday that moving the U.S. embassy to Jerusalem could have "explosive" results and said he was worried that the prospects for a two-state solution to the Israeli-Palestinian conflict were waning. U.S.

BEIJING (Reuters) - Law enforcement and judicial officials in China must be absolutely loyal to the ruling Communist Party, state media said, in the latest warning about loyalty in the wake of the jailing of former domestic security chief Zhou Yongkang.

By Stephen Adler and Sujata Rao DAVOS, Switzerland (Reuters) - Ukrainian President Petro Poroshenko called for a worldwide effort to counter the threat of Russian cyber warfare and urged the United States to "be great again" by demonstrating leadership on issues such as global security. U.S.

By James Pearson SEOUL (Reuters) - North Korea may be preparing to test-launch a new, upgraded prototype of an intercontinental ballistic missile (ICBM), South Korean media reported on Thursday, citing military sources. In his New Year's speech, leader Kim Jong Un said North Korea was close to test launching an ICBM, and state media has said a launch could come at any time.

By Tom Miles and Stephanie Nebehay GENEVA (Reuters) - China will build a "new model" of relations with the United States, President Xi Jinping said on Wednesday in a speech that portrayed China as the leader of a globalized world where only international cooperation could solve the big problems.

By Roberta Rampton and Jeff Mason WASHINGTON (Reuters) - President Barack Obama urged President-elect Donald Trump on Wednesday to keep separate the issue of economic sanctions on Russia from the pursuit of talks to reduce nuclear stockpiles.

By Tom Westbrook SYDNEY (Reuters) - The Australian government said on Wednesday it was not ruling out a future underwater search for a missing Malaysia Airlines passenger jet as families of those on board criticized the decision to suspend the hunt after three fruitless years.