No military forces are maintained by Solomon Islands although a police force of nearly 500 includes a border protection unit. The police also are responsible for fire service, disaster relief, and maritime surveillance. The police force is headed by a commissioner, appointed by the governor-general and responsible to the prime minister. On 27 December 2006, the Solomon Islands government took steps to prevent the country's Australian police chief from returning to the Pacific nation. On 12 January 2007, Australia replaced its top diplomat expelled from Solomon Islands for political interference in a conciliatory move aimed at easing a four-month dispute between the two countries.