Addressing around 1,000 people at a mosque in southern Tehran's lower-middle class Naziabad area, Mousavi said it was the "resistance" of the Islamic republic that had led to these achievements.

"Without independence and resistance, we would have not got nuclear and space technologies," Mousavi, who was prime minister from 1981 to 1989, said as the crowd chanted "Mousavi for the presidency".

In February, Iran sent its first home-made Omid (Hope) satellite into space, carried by a Safir-2 rocket, setting alarm bells ringing among Western powers already at loggerheads with Tehran over its nuclear programme.

Mousavi also took a dig at hardline President Mahnoud Ahmadinejad. He questioned whether the governnment, when "it was making profits from high oil prices, had ever considered a situation that the prices would fall" eventually.

On Tuesday, he announced his candidacy for the June 12 election. That will pitch him against former president Mohammad Khatami and former parliament speaker Mehdi Karroubi, both reformers, and presumably Ahmadinejad, who has yet to formally declare his candidacy.

Since Iran scrapped the post of prime minister when the constitution was revised in 1989, Mousavi has kept a low profile and rarely given interviews.

He is a member of the Expediency Council, the top political arbitration body, and heads Iran's Art Academy, which was established to safeguard the national heritage.

He also served as presidential advisor from 1989 to 2005.

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