The NBA warned a touring group of its stars that they could face financial fines for participating in clinics in Manila, Philippines, that include short scrimmages and games of "H-O-R-S-E," league sources told Yahoo Sports.

Several NBA stars, including Blake Griffin, James Harden, Kawhi Leonard and Damian Lillard, were scheduled to participate in promotional appearances in Manila this week, and the NBA has told its Players Association that the event organizers failed to gain league approval, sources said.

There were scheduled to be two days of exhibition events on Tuesday and Wednesday in Manila, but news reports out of Manila suggest that those events were canceled and ticket refunds were given to fans.

The NBA warned against violations that included "some kind of exhibition of basketball skills," including shooting games and dunk contests, an NBPA memo obtained by Yahoo Sports said.