Indian prisoners stone to death a Pakistani inmate in a jail amid mounting tensions over a suicide bombing that Delhi has blamed on its arch-rival neighbour, an official says.

Saudi Arabia's Crown Prince Mohammed bin Salman is due to arrive in Pakistan at the start of his tour of South Asia and China, but the visit risks being overshadowed by escalating tensions between nuclear-armed rivals India and Pakistan.

As India and Pakistan prepare to celebrate 70 years of independence from Britain, thousands of families in the nuclear-armed neighbours remain divided by a border that strained diplomatic ties make harder to cross.