By Charlotte Greenfield ISLAMABAD (Reuters) -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.

For the first time, India on Wednesday suspended the World Bank-mediated Indus Waters Treaty of 1960 that ensures water for 80% of Pakistani farms, saying it would last until "Pakistan credibly and irrevocably abjures its support for cross-border terrorism".

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.