In March 1992, the start of the UNTAC mission in Cambodia was marked by the arrival of 22,000 UN peacekeepers, which included troops from 22 countries, 6,000 officials, 3,500 police and 1,700 civilian employees and electoral volunteers. The mission was led by Yasushi Akashi. In June 1992, the Khmer Rouge formally established the National Union Party of Kampuchea, and announced that it would not register to participate in the upcoming elections. Furthermore, the Khmer Rouge also refused to disarm its forces in accordance with the Paris agreement. Then, to prevent ethnic Vietnamese from taking part in the elections, the Khmer Rouge started massacring Vietnamese civilian communities, causing hundreds of thousands of Vietnamese to flee Cambodia. Towards the end of 1992, Khmer Rouge forces advanced into Kampong Thom in order to gain a strategic foothold, before UN peacekeeping forces were fully deployed there. In the months leading up to the elections, several UN military patrols were attacked as they entered Khmer Rouge-held territory.