North Korea Tensions, Erdogan's Win in Turkey: The Week in Pictures April 15-21

From tensions rising between North Korea and the U.S., to historic power shifts in Turkey, this is the Week in Pictures.

Fears of an all-out war between North Korea and the U.S. increased this week, as Washington responded to Pyongyang's sabre-rattling with some of its own. After Vice President Mike Pence visited the demilitarized zone separating the two Koreas on April 17, he headed to Japan to reassure the nation and offer some strong words for the isolated regime.

"The era of strategic patience is over and while all options are on the table, President (Donald) Trump is determined to work closely with Japan, with South Korea, with all our allies in the region and with China to achieve a peaceable resolution and the denuclearization of the Korean peninsula," Pence said in Tokyo before lunch with Prime Minister Shinzo Abe.

Pence's comments came after a warning by a senior North Korean official that his government plans weekly tests and an "all-out war" if the U.S. takes any action against it, and has no intention of going slow on its missile program.

The White House also issued some strong words in Turkey this week; Trump called Turkish President Recep Tayyip Erdogan to congratuate him following his slim victory in a referendum that grants him sweeping powers in the biggest overhaul of modern Turkish politics. The vote will replace Turkey's parliamentary system with an all-powerful presidency and abolish the office of prime minister, a move Erdogan said was necessary to secure the nation against terror and outside influence from Europe and the West. Opponents and international monitors have questioned the legitimacy of the vote and some have said the vote was marred by irregularities, but Trump's call sends a message the White House is behind the results.

Erdogan said on Thursday he would meet Trump in Washington on May 16, in their first meeting since Trump took office in January. Ties between the United States and Turkey have deteriorated sharply since a failed military coup in July and disagreements over U.S. support for a Kurdish militia group fighting the Islamic State militant group (ISIS) in Syria. Turkey sees the group as an extension of the outlawed PKK, which has waged a three-decade insurgency for Kurdish autonomy in southeastern Turkey.

Ankara is also pressing for the extradition of Fethullah Gulen, a Muslim cleric living in the United States who is accused by Erdogan of engineering the failed coup.

At the week's conclusion, news broke of an attack in Paris with the ISIS taking credit for the murder of one police officer in a shooting incident on April 20. Masked police immediately took to the streets, blocking access to the Champs-Elysees through the night. The attack comes days before presidential elections. President Francois Hollande said he was convinced the "cowardly killing," in which the assailant was himself shot dead by police, was an act of terrorism.