The UK has called on India and Pakistan to show urgent "restraint" as tensions between the two nuclear-armed rivals in the Kashmir dispute deepen.
Pakistan’s civil aviation authority said it has shut its airspace to all commercial flights as tensions with India escalate.
The announcement came after the nation’s army said its air force shot down two Indian warplanes and captured two pilots after they crossed the boundary in the disputed territory of Kashmir.
Foreign Secretary Jeremy Hunt issued a video appeal for restraint, echoing a message delivered by Prime Minister Theresa May at the start of PMQs in the House of Commons.
Mr Hunt said: "The UK is very concerned about rising tensions in Kashmir between India and Pakistan. Both countries are good friends of the UK."
He said he had been in contact with his counterparts in Pakistan and India, with the message: "We urgently call for restraint on both sides to avoid further escalation."
Major General Asif Ghafoor said Pakistani troops on the ground captured two Indian pilots.
He said one of the planes crashed in Pakistan’s part of Kashmir and the other went down in Indian-controlled Kashmir.
The dramatic escalation came hours after Pakistan said mortar shells fired by Indian troops from across the frontier dividing the two sectors of Kashmir killed six civilians and wounded several others.
Pakistan’s army spokesman Major General Asif Ghafoor said Pakistani troops on the ground captured the pilots. He added that one of the downed planes crashed in Pakistan’s part of Kashmir, while the other went down in Indian-controlled section of the Himalayan region.
The injured pilot is being treated at a military hospital. Maj Gen Ghafoor said the pilots are being treated well, but made no mention of them being returned to India.
He struck a conciliatory tone, saying: "We have no intention of escalation, but are fully prepared to do so if forced into that paradigm."
Indian air force spokesman Anupam Banerjee in New Delhi said he had no information on Pakistan’s statement.
Earlier, senior Indian police officer Munir Ahmed Khan said an Indian air force plane crashed in Indian-controlled sector of Kashmir and that it was not immediately known if there were casualties.
Another police officer, SP Pani, said firefighters were at the site in Budgam area in Indian-controlled Kashmir where the Indian warplane crashed.
Eyewitnesses said soldiers fired into the air to keep residents away from the crash site.
Indian news reports said airports in the Indian portion of Kashmir closed for civilian traffic shortly after the air force jet crashed. The Press Trust of India news agency said these airports are located at Srinagar, Jammu and Leh. Indian authorities declined to comment.