An Iranian court has jailed a prominent human rights activist and journalist for six years after convicting her of "waging war against God" and other charges.

In another indication of the regime's determination to punish those who took part in protests after last year's disputed presidential election, Shiva Nazar Ahari was convicted of the crime known as "moharebeh" - usually punishable by death.

The 26-year-old, who founded the Committee of Human Rights Reporters in Tehran, was also convicted of plotting to commit crimes and agitating against the ruling system, Iran's semi-official ILNA news agency reported.

Ahari was fined about £250 as a substitute for receiving 76 lashes. The activist's family and supporters say the charges were politically motivated.

She was arrested in December on her way to the funeral of Grand Ayatollah Hossein Ali Montazeri, the spiritual mentor of the Green movement, which opposed the re-election of President Mahmoud Ahmadinejad last June. Her supporters have voiced particular objection to the allegation behind the charge of moharebeh, which is that she was a member of the banned Mojahedin e-Khalq group, accused by the Iranian regime of terrorist activities. Her family say she deplores the organisation.

Ahari's lawyer, Mohammad Sharif, was quoted as saying he was "shocked" to learn that his client had been convicted of moharebeh, saying there was "no legal basis for this charge against her". He said he planned to file an appeal. Following her arrest, Ahar was held at the Evin prison, in Tehran, with little access to her lawyer or family members. She reportedly spent long periods in solitary confinement.

Since the disputed presidential election, journalists have become a prime target in the Iranian government's crackdown on the opposition. In a report published in March, the New York-based Committee to Protect Journalists said at least 52 journalists were being held in Iranian jails.

Several other female activists have been targeted since the election. Earlier this month, Nasrin Sotoudeh, a lawyer who has represented several arrested political activists and protesters, was arrested and charged with "propaganda against the regime" and "acting against national security".

Sotoudeh's husband, Reza Khandan, said she had been warned that she would be arrested if she continued to represent Shirin Ebadi, the Iranian Nobel peace prize laureate and human rights activist who left Iran a day before the election.

The opposition insist that June's election was rigged. Authorities in Iran deny the claims and have blamed foreign countries for fomenting sedition.