Pakistan conducted a second missile test and India ordered civil defence drills in an escalating stand-off over contested Kashmir that the UN said on Monday has brought the two nations to the brink of war.

New Delhi blames Islamabad for backing an attack on tourists last month - the deadliest against civilians on the Indian-administered side of the Himalayan territory for years - sparking a series of heated threats and diplomatic tit-for-tat measures.

Pakistan rejects the accusations, and the two sides have exchanged nightly gunfire since April 24 along the de facto border in Kashmir, the militarised Line of Control, according to the Indian army.

UN chief Antonio Guterres on Monday said relations between Pakistan and India had reached a "boiling point", warning that "now is the time for maximum restraint and stepping back from the brink" of war.

The Pakistani military said on Monday it had tested a surface-to-surface missile with a range of 120 kilometres, a launch "aimed at ensuring the operational readiness of troops".

The missile test comes as Iran's top diplomat Abbas Araghchi was in Islamabad for talks with Prime Minister Shehbaz Sharif on Monday, ahead of a visit to India on Thursday.

Tehran has offered to mediate between the two nuclear-armed neighbours, and Araghchi will be the first senior foreign diplomat to visit both countries since the April 22 attack sent relations into a tailspin.

"We will spare no effort to help de-escalate the situation between the two countries," Iranian foreign ministry spokesperson Esmaeil Baqaei said.

Pakistan announced a previous test on Saturday of a surface-to-surface missile with a range of 450 kilometres - about the distance from the Pakistan border to New Delhi.

It has not said where either of the tests took place.

Sharif, who cancelled a visit to Malaysia scheduled for Friday, said the launch "clearly shows that Pakistan's defence is in strong hands".

Indian information ministry officials said that several civil defence "mock drills" would take place on Wednesday, preparing people to "protect themselves in the event of a hostile attack".

Muslim-majority Kashmir, a region of around 15 million people, is divided between Pakistan and India but claimed in full by both.

No group has claimed responsibility for the April 22 killing of 26 mainly Hindu men in the tourist hotspot of Pahalgam, but Indian police are seeking at least two Pakistani citizens they say are among the alleged gunmen. (AFP)