Twitter has suspended the personal account of US senator Mike Lee, after the Utah Republican appeared to the threat the prime minister of Japan over a detained US Navy serviceman.

“My personal Twitter account – @BasedMikeLee – has been suspended,” Senator Lee wrote from his official account on Wednesday. “Twitter did not alert me ahead of time, nor have they yet offered an explanation for the suspension. My team and I are seeking answers.”

Earlier in the day, Mr Lee wrote multiple messages to Japanese prime minister Fumio Kishida on his personal account regarding detained US Navy lieutenant Ridge Alkonis.

"Hand Lt. Alkonis over to U.S. custody immediately," one tweet read.

"If you don’t hand him over in the next seven hours, a series of conversations will begin tomorrow to inform Americans of how poorly you’re treating our military personnel—not just Ridge Alkonis, but all 55,000 U.S. forces in Japan," another said.

This is a breaking news story and will be updated with new information.