The agreement split the Indus and its tributaries between the two countries and regulated water sharing. India was granted the use of water from three eastern rivers - Sutlej, Beas and Ravi - while Pakistan was granted most of the three western rivers - Indus, Jhelum and Chenab.

Pakistan closed its air space for Indian airlines and rejected New Delhi's suspension of a water sharing treaty on Thursday in retaliation for neighbouring India's response to a deadly militant attack in the Indian-ruled part of Kashmir.

The spray of gunfire at tourists Tuesday in a scenic, mountain-ringed valley was the worst assault in years targeting civilians in the restive region.