The anonymous source cannot specify the reason for the explosions, but they come at the same time as India and Pakistan accuse each other of carrying out waves of drone attacks.
Indian authorities reported several civilian deaths during the night, when Pakistan, according to India, launched an attack with drones and robots. India is said to have retaliated by knocking out an air defense system in Pakistani territory.
According to Pakistan, the country's forces killed 40-50 Indian soldiers in a series of attacks on Indian military installations.
India is threatening further "decisive" actions.
Our intention is not to escalate the situation. But military attacks against us will undoubtedly be responded to very, very decisively, said the Indian Foreign Minister Subrahmanyam Jaishankar in a speech.
Drones shot down
The nighttime artillery fire took place, according to the Indian military, across the so-called control line between the northern parts of Kashmir, controlled by Pakistan, and the southern parts controlled by India.
13 civilians are reported to have been killed and 59 injured by Pakistani fire in the city of Poonch, in what Indian authorities call a "violation of the ceasefire" since Wednesday. Pakistan has not confirmed or commented on the reports.
According to Pakistan, the country's air defense has in turn shot down 25 Israeli-made Indian drones over, among other places, Lahore early on Thursday.
Promised "revenge"
It is the second night of heavily escalated violence in the troubled region. The night against Wednesday, India carried out airstrikes against Pakistan-controlled areas in Kashmir. According to Pakistan, around 30 civilians were killed, while India has described it as a robot attack on nine Pakistani "terrorist camps".
Pakistan's Prime Minister Shehbaz Sharif said in a speech to the nation late on Wednesday that Islamabad would "avenge" those killed by India.
The tensions between the two nuclear-armed nations have increased sharply in recent weeks, since a massacre of tourists on April 22 in the Indian-controlled part of the long-disputed Kashmir region. India accuses Pakistan of having given its support to the perpetrators, which is denied by the country.
