A truck driver has been arrested after a young man was killed in a suspected hit-and-run in the Sydney CBD.

Emergency workers were called to Central St about 1.30am on Wednesday after the 21-year-old man was found dead.

Three hours later police stopped a truck at Kings Cross and arrested the 52-year-old driver.

He has been taken to Day St Police Station and a crime scene has been set up at the site of the crash.