Convoys of go-karts reminiscent of Nintendo Co.'s "Mario Kart" video game series have been turning heads in Tokyo's traffic, but the rental companies behind them, which cater mostly to foreign tourists, are facing growing scrutiny over their safety records.

Tourists dressed as Mario and other characters from the video game drive through often-crowded public streets in the low-riding vehicles.

Although they are operated in line with the law, the central government has raised concerns about the lack of safety measures being taken by five Tokyo-based operators following a spike in go-kart accidents in recent months.