He made the annoucement in Srinagar after undertaking a visit to the state for first hand information of the situation which has turned grim resulting in the death of over 130 people.
The Prime Minister also called upon other states to also pitch in with relief assistance in whatever way they could.
Expressing his anguish at the loss that has been caused in neighbouring areas in Pakistan-Occupied Kashmir (PoK), he said India was ready to provide humanitarian assistance to the affected areas if Pakistan requires it.
"The Prime Minister shared the pain and anguish of the people as he was briefed in Jammu and in Srinagar by Chief Minister Omar Abdullah and senior officials of the state government about the damage caused by the floods," a PMO statement said.
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The Prime Minister observed that the Rs 1100 crores which is being made available to the state government through the state Disaster Relief Fund would not prove to be adequate in view of the magnitude of the tragedy.
Terming it as a national level disaster, Modi said that the centre stands shoulder to shoulder with the state government and the people of the state in this hour of crisis.