Iran's permanent representative to the International Atomic Energy Agency (IAEA) Ali-Asghar Soltanieh said the Islamic republic and the UN nuclear watchdog have agreed to hold new round of talks on Iran's nuclear issue on May 13-14, the official IRNA news agency reported on Saturday.

In an interview with IRNA on Friday, Soltanieh said the talks with the agency will encompass setting framework and modality for responding to some IAEA questions relevant to Iran's nuclear activities.

It has been agreed that the next round of talks will be held in Iran's permanent representative office in Vienna, the report quoted Soltanieh as saying.

The remarks by the Iranian official came as the latest round of nuclear talks between Iran and six world powers -- Britain, China, France, Russia, the United States plus Germany (P5+1) -- concluded in Turkey's Istanbul earlier this month, with all sides describing the talks as positive and agreeing to meet again in Baghdad on May 23.

In March, the IAEA head Yukiya Amano said that Iran had stepped up its nuclear enrichment activities, as its monthly production of 20-percent purity uranium had tripled since November 2011.

Speaking at the quarterly meeting of the IAEA board, Yukiya Amano said the UN nuclear watchdog had "serious concerns" that Iran's heightened enrichment activities might relate to the development of nuclear weapons.

Amano also highlighted Iran's repeated refusal to allow inspectors into Parchin military site, in which simulated nuclear warhead tests allegedly took place.

Earlier, Soltanieh said that access to Parchin would only be granted if Iran and the IAEA agree on certain conditions.