An informed Japanese source said Tuesday that the number of foreign visitors that attended North Korea's mass gymnastic festival "Arirang" since it opened April 29th is estimated at about 18,000. The source said, however, that exactly how many foreign tourists, besides overseas Koreans, witnessed the extravaganza has yet to be known. The source said attendance at the festival by foreign travelers is known to have fallen far short of original expectations. The North said Tuesday that the show would continue past its second closing date of July 15th due to continued "domestic demand. No closing date for the festival, termed a "once-in-a-millennium event" by the North, was announced.