The chief of the U.S. Federal Bureau of Investigation(FBI) said on Tuesday that North Korea, China and Russia are employing cyber operations to target U.S. research.

FBI Director Christopher Wray made the remarks in a statement prepared for a session of the Senate Committee on Homeland Security and Government Affairs, saying that cybercriminal actors continue to innovate by using unique techniques to compromise U.S. networks.

Wray said that his agency has seen China working to obtain controlled dual-use technology while developing a range of advanced cyber capabilities deployable against other countries in the event of a real conflict.

The FBI chief said there is growing concern about the ability to detect cyber operations against U.S. organizations as hostile actors develop more sophisticated methods, stressing the need to elevate the difficulty and punishment for carrying out such cyber activities.

As for intelligence threats, Wray said that China, Russia and Iran are becoming "more aggressive and more capable than ever before,” adding the greatest long-term threat to the U.S.’ ideas, innovation and economic security is the threat of foreign intelligence and economic espionage by China.