"Those responsible and behind such an act will very soon hear our response, loud and clear," Rajnath Singh said in a speech in New Delhi, a day after gunmen killed 26 men at a tourist hotspot in the Himalayan region.

"We won't just reach those people who carried out the attack. We will also reach out to those who planned this from behind the scenes on our land."

Singh did not identify those who India believes are responsible for the killings, but said that "India's government will take every step that may be necessary and appropriate".

No group has claimed responsibility but rebels in the Muslim-majority region have waged an insurgency since 1989.

They are seeking independence or a merger with Pakistan, which controls a smaller part of the Kashmir region and, like India, claims it in full.

India regularly blames Pakistan for backing gunmen behind the insurgency. Islamabad denies the allegation, saying it only supports Kashmir's struggle for self-determination.

Pakistan's foreign ministry on Wednesday offered its "condolences to the near ones of the deceased".

Indian Prime Minister Narendra Modi, in a statement shortly after the attack, pledged that those responsible for the "heinous act" will "be brought to justice".

Modi is set to hold an emergency cabinet meeting with top security chiefs later on Wednesday.