An Indian airforce helicopter crashed in a remote mountain area near the border with China on Friday, killing all seven troops on board, officials said. The Russian-made Mi-17 helicopter was ferrying military officials to a forward post in the northeastern state of Arunachal Pradesh, defense spokesman Suneet Newton said. The crash happened in Tawang, which is also claimed by China. Tawawng is a strategically important border district and came briefly under Chinese control during the 1962 war between the two neighbouring countries.  Indias Air Force has a high rate of crashes owing to its ageing fleet. More than 170 pilots have lost their lives over the last three decades. India is spending billions of dollars trying to modernise its airforce with new planes and helicopters but the procurement process has been slow. Newton said the cause of Fridays crash was not known immediately. India has also been expanding its military infrastructure in the area to narrow the gap with China which has superior road and air links.