Mohammad Ali Abtahi faces six years in jail after being accused of fomenting unrest after disputed June election in Iran

A former Iranian vice president has been sentenced to six years in jail after being accused of fomenting unrest to overthrow the government, his lawyer said today.

Mohammad Ali Abtahi is the most senior reformer to face imprisonment following the disputed presidential election in June. Abtahi was vice president for parliamentary and legal affairs during the 1997-2005 presidency of Mohammad Khatami.

The lawyer, Saleh Nikbakht, said he planned to appeal against the verdict. He has 20 days to submit the appeal. Abtahi was released on $700,000 (£425,000) bail after the verdict was delivered.

As news of the latest sentence emerged, the opposition leader, Mir Hossein Mousavi, called on the government to stop intimidating people.

"The government should not intimidate people to change their path … this movement will continue and we are ready to pay any price," Mousavi was quoted as saying on his Kaleme website.

Mousavi's remarks coincided with a gathering by moderates to commemorate the killing of a dissident nationalist couple, stabbed to death by "rogue" agents in 1998. The killing of Dariush Forouhar and his wife, who headed the illegal but tolerated Iran Nation party, and at least two other secularist figures, outraged Iranian society.

Iran's security forces have warned the opposition not to take part in demonstrations, in an attempt to avoid a revival of the protests that erupted after the presidential elections on 12 June in which President Mahmoud Ahmadinejad secured a second term. The turmoil after the election was the worst in Iran since its 1979 Islamic revolution. Authorities deny vote-rigging and portrayed the unrest as a foreign-backed bid to undermine the Islamic state.

A key part of the government's strategy has been the mass trial of reformist political figures accused of supporting the post-election unrest and seeking to topple the regime through a "velvet revolution".

Abtahi's daughter, Fatemeh Abtahi, was quoted by Kaleme as saying that security agents searched her father's Tehran home in his presence yesterday, after which he was taken to a court where he was told about his sentence and then returned to jail.

Abtahi made televised confessions after his arrest in which he admitted provoking people to riot. His family and fellow reformers said the confessions were obtained under duress. Abtahi was a top adviser to pro-reform cleric Mehdi Karoubi, who finished fourth in the presidential elections. Kaleme said his lawyer would seek his release on bail.

Iran's judiciary said last week that five people have been sentenced to death and 81 have received jail terms of up to 15 years in connection with protests and violence after the poll, but it did not give their names.

The head of a hardline political party, Mohammad Nabi Habibi, called yesterday for Mousavi to face trial for spreading the "big lie" of vote fraud. Any legal action against Mousavi, who came second in the election, could trigger new street protests by his backers.

Meanwhile Iran's military has said it will begin large-scale air defence drills today, with a cleric in the Revolutionary Guards warning that the Islamic Republic would fire missiles at "the heart of Tel Aviv" if attacked. The war games, due to last five days, are intended to help protect Iran's nuclear facilities, according to Iranian media.

The declaration came as a UN committee voted to approve a non-binding resolution condemning Iran for its crackdown on protesters following the presidential elections. The resolution also repeated annual criticism of Iran's human rights record, including the use of torture and an increasing execution rate.

Iran's UN ambassador, Mohammad Khazaee, dismissed the resolution as politically motivated.