The Israeli military identified the assailant as 17-year-old Muhammad Tarayra, and described him as a "terrorist."
Prime Minister Benjamin Netanyahu said the "entire world needs to condemn this murder" just as it condemned terror attacks in Orlando and Brussels.
"The horrifying murder of a young girl in her bed underscores the bloodlust and inhumanity of the incitement-driven terrorists that we are facing," he said in a statement. "The entire nation deeply identifies with the family's pain and declares to the murderers: You will not break us."
The U.S. State Department decried the "outrageous terrorist attack" and extended condolences to the victim's family.
"This brutal act of terrorism is simply unconscionable," it said in a statement.
Germany's Foreign Office also condemned the attack, saying on Twitter: "Nothing justifies the murder of a sleeping child."
#Germany strongly condemns the murder of a 13-year-old #Israeli girl in the #WestBank: Nothing justifies the murder of a sleeping child.
Cassandra Vinograd is a Senior Writer and News Editor. Before joining NBC News, she worked as a London-based correspondent for The Associated Press and specialized in politics, foreign affairs and defense.
Vinograd previously worked as an editor for The Wall Street Journal in Brussels and London.
She has reported extensively from Afghanistan and on West Africa and the Middle East.