TEHRAN - Iran on Wednesday stepped up its campaign against dissenters, shutting down a reformist newspaper as the election watchdog declared the June 12 election presidential results to be final.

The government halted the publication of Etemad Melli after its defeated presidential candidate Mehdi Karroubi said the re-election of Mahmoud Ahmadinejad was invalid and that he did not consider his government legitimate.

The 12-member Guardians Council election watchdog warned defeated candidates that it will brook no more challenges to the results following a recount of 10 percent of ballot boxes.

Supporters of Mir Hossein Mousavi, Ahmadinejad's closest rival who won 34 percent of the vote compared to 63 percent for the incumbent, remained defiant, reiterating a demand for the cancellation of the vote.

Iran is still holding one local staff member from the British embassy out of nine who were detained on allegations of stoking the unrest, state-run Press TV reported.

Iran's police chief Esmaeil Ahmadi-Moghaddam said that 20 people were killed and more than 1,000 arrested in the wave of protests over the disputed presidential poll.

"No policeman was killed in the Tehran riots but 20 rioters were killed," he said, confirming earlier reports.

"Police arrested 1,032 people in the recent riots. Many have been released and the rest are being prosecuted in Tehran's public and revolutionary courts," he was quoted as saying by the Fars news agency.

The Paris-based International Federation for Human Rights has said that more than 2,000 people are in custody in Iran and hundreds more missing, while rights group Amnesty said it was concerned that several detained opposition leaders may face torture.

Human Rights Watch said on Wednesday that harsh interrogation conditions and inadequate medical care are threatening the life of detained reformist Saeed Hajjarian, a former presidential adviser and Tehran city councillor.

Ahmadi-Moghaddam said the death of Neda Aqa-Soltan, who became a symbol of post-election street rallies in Iran, was a "prearranged scenario," Press TV reported.

The police chief accused Arash Hejazi, a doctor who says he tried to save Neda's life in her final moments, of fanning the flames of the western media hype, the TV station said on its website.

Ahmadinejad on Wednesday cancelled a trip to Libya, where he was due to have addressed a summit of African leaders in the seaside town of Sirte at the invitation of Libyan leader Moamer Kadhafi.

The planned visit had heightened tensions at the summit where delegates said Kadhafi had extended the invitation without consulting the 53-member bloc.

No reason was given for the last minute cancellation and it was impossible to know whether Amhadinejad's pullout was connected with the wave of opposition which has swept Iran since the election which has triggered the worst crisis since the Islamic revolution in 1979.

The authorities have moved quickly to suppress public demonstrations and have rounded up scores of reformists and political activists in the wake of the disputed election.

One of them is Mohammad Ghoochani, chief editor of Etemad Melli, the newspaper owned by the party of the same name which was banned on Wednesday.

The foreign media remains banned from reporting from the streets under tough new restrictions imposed in the violent election aftermath.

British Prime Minister Gordon Brown on Wednesday expressed "deep disappointment" at the behaviour of Iranian authorities since the election.

During his weekly question and answer session with lawmakers in the House of Commons, Brown condemned the arrest of the nine embassy employees.

"This action is unjustified and it is unacceptable and some people in Iran are trying to seek to use Britain as an explanation for the legitimate Iranian voices calling for greater openness and democracy," he said.

EU countries are considering a proposal from Britain for a temporary recall of all of their ambassadors from Iran in protest at the detention of the British embassy employees by Tehran, a European diplomatic source said.

"The British proposal is doing the rounds amongst the EU member states... We should know more on Thursday when a meeting is set to be held in Stockholm between the political directors of the (different European) foreign ministries," the source said.

The source said no deal on a recall had been reached as yet, while another European diplomatic source admitted it would be difficult for all 27 EU member states to agree on such a measure.