Addressing a special cabinet meeting here to discuss the situation in Kashmir, Sharif termed the "movement of Kashmiris as a movement of freedom".
"The whole Pakistan is standing by Kashmiris. Pakistan would continue to extend moral, political and diplomatic support for Kashmiris in their just struggle for right to self-determination," the Sharif said.
"The Prime Minister termed Burhan Wani as martyr of independence movement," Radio Pakistan reported.
He said, the "Indian brutalities will give impetus to the freedom struggle and Kashmiri people will get their right to self-determination for which the whole Pakistani nation is standing behind them."
Sharif directed all the relevant departments to highlight the Kashmir issue at international fora.
The cabinet decided that "black day" will be observed on Tuesday (July 19).
An official statement released after the meeting said, "July 19 will be observed as a black day in the country so that the attention of the international conscience can be drawn towards the atrocities of Indian forces in Kashmir."
The cabinet asked the United Nations to renew its efforts to complete its "unfinished agenda" and ensure implementation of its resolutions "so that Kashmiris get their right of self determination."
It said the Kashmiri leadership should be involved in the talks between Pakistan and India over Kashmir issue.
Sharif also announced to convene a joint session of the parliament to discuss the situation in Kashmir.
Pakistan Information Minister Pervaiz Rashid said the cabinet meeting was exclusively called to develop a consensus on extending full support to the Kashmiris.
Meanwhile, Pakistan briefed the ambassadors of African and Middle Eastern countries over the tense situation in Kashmir.
"Pakistan's serious concern over the brutal killings of innocent civilians and violation of their fundamental human rights by the Indian forces was conveyed," Foreign Office spokesman Nafees Zakaria said in a statement.
Sharif had earlier deplored "excessive" force against civilians in the latest wave of violence in the Valley while expressing "deep shock" over the killing of Wani.
Sharif, who recently returned from London after an open-heart surgery, had said that it was "deplorable that excessive and unlawful force was used against the civilians" who were protesting against the killing of Wani.