A blast was heard in Pakistan's Lahore city on Thursday, broadcaster Geo TV and a Reuters witness said, a day after Indian strikes on multiple targets in the country and fears of a larger military conflict between the nuclear-armed neighbours.
There was no immediate word on the reason for the blast.
India hit "terrorist infrastructure" in Pakistan in the early hours of Wednesday, two weeks after it accused the Islamic nation of involvement in an attack in Indian Kashmir in which 26 people - mostly Hindu tourists - were killed.
Islamabad had denied the accusation and vowed to retaliate to the missile strikes, also saying it shot down five Indian aircraft. The Indian embassy in Beijing termed reports of fighter jets being shot down as "misinformation".
Pakistan says at least 31 of its civilians were killed and about 50 wounded in the strikes and in cross-border shelling across the frontier in Kashmir that followed, while India says 13 of its civilians died and 59 were wounded.
Ali Aftab, a resident of Lahore that is about 25 km from the Indian border, said he heard a "buzzing sound" followed by an explosion around 7 am (0200 GMT).
"Immediately I rushed to the rooftop and saw smoke rising...the area was cordoned off by security forces soon after the incident," he said.
The Indian defence ministry did not immediately respond to a request for comment but an Indian defence official, who did not want to be named, said there were no Indian operations underway in Lahore.
The cross-border exchange of fire in Kashmir tapered off slightly overnight, Indian officials said.
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