Tokyo police have stepped up measures to prevent a Halloween crowd crush in the bustling Shibuya district, following Saturday's stampede in Seoul that left more than 150 people dead.

Security has been beefed up in Shibuya, which has already attracted crowds this weekend.

Police warn of possible danger if a crowd were to gather around Shibuya Station at night and move slowly in one direction. If some people in the crowd stopped, those behind them could fall over one another.

Officers were urging people to keep moving on the sidewalks on Saturday night, as some paused to take photos.

Those deployed to the district include riot police and a public relations unit known as the "DJ Police" to guide pedestrians.

Officers will further step up their alert on Monday when larger crowds are expected.