British nationals have been warned against travelling to parts of India and Pakistan after a dramatic surge in violence between the two nuclear-armed neighbours left at least 19 people dead. The UK’s Foreign, Commonwealth and Development Office (FCDO) updated its travel advice after India launched air strikes across the Line of Control into Pakistani-administered territory in what it claimed was retaliation for last month’s deadly massacre of tourists in Indian-controlled Kashmir.

Officials in New Delhi said missiles had struck nine targets, including alleged militant infrastructure in Pakistan-administered Kashmir and Punjab province. In response, Pakistan reportedly fired artillery shells into Indian-controlled territory, with seven civilians killed and 30 more wounded, according to the Indian army. The UK Government is now advising against all travel within 10km of the India-Pakistan international border, 10 miles of the Line of Control, and across Pakistan’s volatile Balochistan province.

Flights to and from the region have also been thrown into chaos, with airspace closures forcing airlines to divert or cancel routes.

A Foreign Office statement said: “On the night of 6 May (UK Time), the Indian Ministry of Defence stated it had struck nine sites in Pakistan and Pakistan-administered Kashmir. In response, there are reports of Pakistani artillery fire across the Line of Control.”

The statement added: “Pakistan Civil Aviation Authority indicated that it was closing Pakistan airspace for at least 48 hours. There are reports of flights being diverted. British nationals should contact their airline for up-to-date information.”

The FCDO said it was “continuing to monitor the situation closely” and urged British nationals in the region to follow local advice and remain alert.

The crisis has sparked condemnation and alarm from across the UK political spectrum. First Minister of Scotland John Swinney said he was “deeply concerned by the events in Kashmir” and appealed for “calm and dialogue to avoid further conflict”.

Labour MP Stella Creasy said: “The world cannot stand by as the conflict spirals and the risk of harm to civilians in the region increases. Restraint by all concerned must be sought and secured.”

Former Conservative Foreign Office minister Lord Ahmad said the situation was on a knife-edge, warning: “The potential of a war tonight is real – we need urgent international engagement to prevent a widening of this conflict which carries serious implications not just for the region but for the wider world.”

Pakistani officials claimed the Indian strikes had hit sites linked to banned militant groups, including the Subhan Mosque in Bahawalpur, Punjab, where 13 people – including a child – were reported dead. The claims were made by Dr Zohaib Ahmed, a local medic treating the wounded.

Pakistan’s Prime Minister Shehbaz Sharif condemned what he called “cowardly attacks” and said a “robust response” was already underway. He has convened a meeting of the country’s National Security Committee.

“Pakistan has every right to give a robust response to this act of war imposed by India, and a strong response is indeed being given,” Mr Sharif said.

Pakistan’s military spokesperson, Lieutenant General Ahmed Sharif, said the Indian strikes had targeted six sites in Pakistan-administered Kashmir and three in eastern Punjab.

Indian officials said the strikes were aimed at infrastructure used by militants behind the Pahalgam massacre – a claim Pakistan denies. Islamabad insists there is no conclusive evidence linking it to the attack and has branded the Indian strikes a violation of international law.

Independent MP Zarah Sultana condemned what she described as India’s “unprovoked strike” and warned the escalation represented a “grave threat to regional peace”.

There are conflicting reports of retaliatory action. Pakistan’s state broadcaster claimed its air force had shot down five Indian fighter jets, though there was no immediate response from New Delhi.

The United Nations also weighed in. Spokesman Stephane Dujarric said Secretary-General Antonio Guterres was “deeply concerned” and urged both sides to show “maximum military restraint”.

He warned: “The world cannot afford a military confrontation between India and Pakistan.”