An Asia-Pacific security summit in Singapore has been placed under lockdown after police shot a man dead in an apparent drug-related incident outside the venue, according to a police statement.

Police said they opened fire after a car with three persons which was stopped at a checkpoint before dawn on Sunday suddenly accelerated despite warnings to stop, crashing through police barricades.

After police opened fire, one man was killed and two were detained.

The Shangi-La Dialogue security conference, a major event in the Asia-Pacific region attended by US Defence Secretary Ash Carter and delegates from dozens of countries from around the world, was uninterrupted but access to the venue was restricted.

"Substances believed to be drugs were found on one of the persons detained," the police statement said.

"Due to the ongoing Shangri-La Dialogue, security measures including vehicle and person checkpoints have been put in place in the vicinity of the Shangri-La Hotel," the statement said.

Source: Agencies