The first day also saw the Syrian delegation walking out of the speech by Egyptian President Mohammad Morsi, who described the Bashar al-Assad regime as "oppressive."
Host Iran, which assumed the chairmanship of the NAM for a period of three years, used the platform to demonstrate that it is not internationally isolated and to launch a scathing attack against the US and Israel.
Khamenei asserted Iran's right for nuclear energy and called for a "Middle East free of nuclear weapons."
"Iran considers the use of nuclear, chemical and similar weapons as a great and unforgivable sin," he said, adding that "this does not mean forgoing our right to peaceful use of nuclear power and production of nuclear fuel".
PM Singh's speech stayed clear of the nuclear stalemate but was broadly in tune with the sentiments expressed by the Iran - that there should not be external intervention in Syria and sympathetic to the "long suffering people of Palestine."
"As the world's largest democracy, India supports popular aspirations for a democratic and pluralistic order. Nevertheless, such transformations can't be prompted by external intervention, which exacerbate the suffering of ordinary citizens. NAM should urge all parties to recommit themselves to resolving the crisis peacefully through a Syrian-led inclusive political process," PM said.