Cambodian police Thursday surrounded an international school in the country's northwest, where up to 40 young students and a handful of teachers were being held hostage by masked gunmen, a government spokesman was reported by dpa as saying. A parent at the scene had earlier said they feared 20 children in the kindergarten classes of the British International School in Siem Reap were being held, but government spokesman Khieu Kanharith said official estimates were now closer to 40. "The men are masked, so we do not know who they are," Kanharith said when asked about their motives. "They are not demanding money, however. They have so far asked for eight AK-47 (assault rifles), some rocket launchers and a minivan." "The negotiations are now being hampered by the fact that they have switched off their phone. Maybe their motive is just to disrupt tourism in Siem Reap." The school is near the famed Angkor Wat temple complex, Cambodia's most important tourist attraction. The children at the center of the drama are from a number of countries including Cambodia, Japan and Korea, although exact nationalities were still unclear. They were believed to be unharmed as the drama entered its fifth hour after the men stormed the school building at around 9.30 a.m. local time. --SP 1008 Local Time 0708 GMT