Pakistan is preparing international legal action over India's suspension of a key river water-sharing treaty, a government minister told Reuters, as tensions intensify between the neighbours following an attack on tourists in India-administered Kashmir.

India blames Pakistan for an attack on its tourists and threatens to disrupt Pakistani water supplies. Islamabad says that move would be an act of war.

India and Pakistan are exchanging fire over their de-facto border since the Kashmir attack, but in New Delhi and Islamabad political foes are coming together and looking to score points.