The invite was handed over to Singh by Iranian Foreign Minister Ali Akbar Salehi when he met him here as the Special Envoy of the President.
There was no confirmation whether the Prime Minister will travel to Iran to attend the Summit of 120 member-countries.
Sources said a decision on whether the Prime Minister will attend the Summit will be taken later.
India has been facing intense US pressure for reducing its engagement with Iran, particularly oil imports, in view of sanctions imposed by some countries.
However, External Affairs Minister S M Krishna had yesterday made it clear that Iran is a "key country" for meeting India's energy needs and that the US pressure to reduce oil imports from Iran will not impact its "legitimate" trade ties.
After his talks with Salehi, Krishna had said while India abided by the UNSC resolutions on Iran, unilateral or regional sanctions tend to impact on the market in a globalised world.
"As far as other sanctions, those decided either unilaterally or regionally, we are aware of such measures. In a globalised world, such actions tend to impact on the market and our commercial entities take these into account. Such measures should not impact legitimate trade interests," he had told reporters here with Salehi by his side.
