Hackers linked to North Korea's surveillance authority are believed to have sent threats to Sony Pictures Entertainment Inc. executives using an Internet Protocol address in Shenyang, northeastern China, a diplomatic source familiar with U.S. investigations said Wednesday.

The United States is apparently requesting that the Chinese government provide information on the IP address, as it would be strong evidence to show the involvement of North Korea's General Reconnaissance Bureau in the cyberattack on the U.S. unit of Japan's Sony Corp.

An IP address is a numeric code assigned to a computer connected to the Internet.