His comments came after the Indian government decided to repeal Article 370 of the Constitution which gives special status to Jammu and Kashmir.
Condemning the move, Sharif called on the Pakistani leadership to immediately demand an emergency session of the UN Security Council and to consult with China, Russia, Turkey, Saudi Arabia and other countries over the latest development, Geo News reported.
The opposition leader in his statement offered Pakistan's "unwavering support to the Kashmiri brethren" and said the "people of Kashmir would not be left alone in this adversity".
The PML-N leader also called for an emergency meeting of the parliamentary leaders. "This is a matter of Pakistan's national interest and the entire nation is united on this front."
Condemning the decision, Pakistan Peoples Party Chairperson Bilawal Bhutto Zardari tweeted: "Atrocities in Indian-occupied Kashmir (IoK) unabated. Extremist Indian govt's intentions clear. President must immediately summon Joint session of Parliament in wake of Indian aggression in IoK."
Special Assistant to Prime Minister on Information and Broadcasting Firdous Ashiq Awan said Pakistan "will continue extending moral, diplomatic and political support to the Kashmiris until they achieve their right to self-determination under the UN Security Council resolutions".
In a series of tweets on Monday, she said that India "must not forget that the nation struggling for its just cause cannot be defeated by any gun, tyranny or conspiracy".
Awan added that the international community would have to prove its respect for democracy by supporting Kashmiris.
Pakistan Prime Minister Imran Khan on Sunday said that Islamabad will respond to any "misadventure or aggression" by Indian forces against it.
Khan alleged that India has used "cluster bombs" on civil along the Line of Control and called on the UN Security Council to take note of the "international threat to peace and security".
( With inputs from IANS )