Multiple loud explosions were heard in several places in Pakistan and Pakistani Kashmir on Wednesday as India said it had attacked "terrorist infrastructure" in nine sites and Pakistan vowed to respond to the attacks.

After the explosions, power was blacked out inMuzaffarabad, the capital of Pakistani Kashmir, witnesses said. It was not immediately clear what the explosions were.

"A little while ago, the Indian armed forces launched 'OPERATION SINDOOR', hitting terrorist infrastructure in Pakistan and Pakistan-occupied Jammu and Kashmir from where terrorist attacks against India have been planned and directed," the Indian government said in a statement.

"Our actions have been focused, measured and non-escalatory in nature. No Pakistani military facilities have been targeted. India has demonstrated considerable restraint in selection of targets and method of execution," it said.

A spokesman for Pakistan's military told broadcaster ARY that India had attacked Pakistan with missiles in three places and that Pakistan would respond.

The development comes amid heightened tensions between the nuclear-armed neighbours in the aftermath of an attack on Hindu tourists in Indian Kashmir last month.

India blamed Pakistan for the violence in which 26 men were killed and vowed to respond. Pakistan denied that it had anything to do with the killings and said that it had intelligence that India was planning to attack.