“It is regrettable that Iran has yet to reach agreement with the IAEA on a plan to resolve all outstanding issues,” the spokesperson told a news briefing at UN Headquarters in New York.

According to media reports, a leaked quarterly report from the IAEA notes that Iran has doubled the number of uranium enrichment centrifuges it has in an underground bunker.

Meanwhile, Iran has also yet to allow the IAEA to visit a military site at Parchin, where the agency suspects Iran carried out explosives testing that it is now working to cover up, which has “significantly hampered” the agency’s investigation efforts.

The Iranian nuclear issue was a topic of discussion in the UN chief’s various meetings in Tehran, where he attended the 16th Summit of the Non-Aligned Movement (NAM). The Summit, under the chairmanship of the Government of Iran, in the Iranian and drew representatives from its 120 members, as well as from various associated observer countries.

Iran’s nuclear activities have been of international concern since the discovery, in 2003, that Iran had concealed its nuclear activities for 18 years, in breach of its obligations under the Nuclear Non-Proliferation Treaty. Iran has repeatedly stated that its nuclear programme is for the peaceful purpose of providing energy.

In a statement in the Tehran summit Iran’s Supremem leader said: “I stress that the Islamic Republic has never been after nuclear weapons and that it will never give up the right of its people to use nuclear energy for peaceful purposes.” But Israel, the United States and their allies in Europe  believe Iran is developing atomic weapons.

In a meeting on Thursday, with the Iranian Foreign Minister, Aliakbar Salehi, Mr. Ban had shared his concern about Iran’s nuclear programme and underscored the importance of transparency in this matter, as well as the need for Iran to fully comply with the IAEA.

He added that he has condemned threats by any Member State to destroy or delegitimize another. “And I have reminded leaders here – and indeed throughout the region – to lower the volume and stop the provocation that can lead this area down a slippery slope of conflict. It is time for more reason and responsibility,” Mr. Ban said.

Ban’s remarks come after Iranian remarks earlier this month threatening Israel’s existence. Iran’s president Mahmoud Ahmadinejad called Israel a “cancerous tumour” with no place in a future Middle East, were “outrageous and hateful” while Iranian media had earlier reported that Iran’s Supreme Leader Ayatollah Ali Khamenei had said Israel would one day be returned to the Palestinian nation and would cease to exist.

The Iranian remarks come as a series of Israeli media suggest that Israel could attack Iranian nuclear facilities ahead of U.S. presidential elections in November.

On the outskirts of Damascus, regime forces shelled rebel strongholds from before dawn on Monday. Activists said more than 45 people including 36 civilians had been killed in the past 48 hours in the area, Al Jazeera reported.

Fighting also raged in the city of Aleppo. Several parts of the Salaheddin neighbourhood where rebels fled last week but has seen continued clashes, are still being bombarded by regime forces, the bombardment has not stopped since morning, according to UK-based  Syrian Observatory for Human Rights. Syrian troops were also advancing on the southwestern rebel stronghold of Sukari in Aleppo, activists reported.

Meanwhile, in the eastern province of Deir Ezzor, opposition rebels reported they shot down a government warplane on Monday while it was bombarding the area.

An amateur video posted on YouTube by activists marked with a logo: “The revolutionary youth from the land of the Euphrates,” shows a fighter jet  being shot, after the sound of heavy bombardment being heard.  Another video on Yotube shows footage of the captured  pilot of the fighter jet, Colonel Mohammed Suleiman, who was taken captive by the rebels.

State new Agency SANA, however, reported that the plane crashed due to technical problems during a “regular training mission”  and said the pilot had ejected from the plane before it crashed.

If confirmed, it would be the first time that the rebels have succeeded in downing a Syrian plane 

In recent months the government has begun to use its air force to try to crush a 17-month-old uprising.

Meanwhile, the foreign ministers of the Gulf Cooperation Council countries and other Arab leaders met in Jeddah, Saudi Arabia on Sunday ahead of the Organisation of Islamic Cooperation (OIC) summit in Mecca on Tuesday.

Iranian President Mahmoud Ahmadinejad will attend the summit, with the Syrian crisis expected to top the agenda, Iranian media said on Monday as Tehran and Riyadh have taken opposing stances on the syrian issue