Towards the end of the war, as Sri Lankan government forces advanced deeper into Tamil Tiger controlled areas, international concern grew for the fate of the 350,000 civilians trapped. On 21 January 2009, the Sri Lankan military declared a 32 square kilometres (12.4 mi) "Safe Zone" located northwest of Puthukkudiviruppu, between the A35 Highway and the Chalai Lagoon. Sri Lankan Air Force aircraft dropped leaflets urging civilians to relocate to the safe zone and wait until the army could move them into safer locations. The Sri Lankan military promised not to fire into the area. However, only small numbers of civilians actually crossed into the Safe Zone, and the Sri Lankan government, the United Nations, and human rights organisations accused the LTTE of preventing civilians from leaving. The fighting eventually caused civilians to flee the safe zone to a narrow strip of land between Nanthi Kadal and the Indian Ocean. The Sri Lankan military declared a new Safe Zone northwest of Mullaitivu on 12 February. Over the next three months, the Sri Lankan military repeatedly attacked the Safe Zone with aircraft and artillery to destroy the last remnants of the Tamil Tigers trapped there. The Sri Lankan government claimed that it was trying to hit Tamil Tiger positions, and claimed that these raids started on 15 February and ended on 19 April, the day before the Army breached Tamil Tiger defences, and civilians started to pour out. However, these attacks caused heavy damage. Thousands of civilians were killed or injured, and the Tamil Tigers reportedly held many as human shields.