Iranian President Mahmoud Ahmadinejad will visit Beijing next month, a spokesman for the Islamic republic's embassy said Wednesday, amid an escalating crisis over Tehran's nuclear programme.

Ahmadinejad will be in the Chinese capital for a meeting of the Shanghai Cooperation Organisation, a Central Asian grouping headed by Beijing and Moscow, said spokesman Mohammad Ali Ziaei.

"Yes, it has been confirmed. The exact date of arrival is not set, but for sure the president will be here on June 7," the spokesman said, giving no further details.

Russian President Vladimir Putin will also attend the June 6-7 gathering, to be chaired by China's President Hu Jintao.

Tehran insists that its nuclear programme is for peaceful use, but it faces a raft of sanctions from the United Nations, the United States and the European Union over suspicions that it is trying to develop atomic weapons.

China, a close ally of Iran, has criticised the measures.

Ahmadinejad last visited China in 2010, when he attended the World Expo in Shanghai.

Iran has observer status in the Shanghai Cooperation Organisation, which groups China, Russia, Kazakhstan, Kyrgyzstan, Tajikistan and Uzbekistan and focuses on regional issues including anti-terrorism.