Today, activists will rally outside 10 Downing Street to press the British Government to step up pressure on Mr Karimov, while human rights groups are lobbying Washington and Brussels to get tough with Tashkent over the incident, which has come to be known as the Andijan massacre.
The killings have divided the international community and seen Uzbekistan, a strategically important, gas-rich central Asian country that borders Afghanistan, become a pariah state in the West. The European Union and the United States have expressed grave doubts about the legality of the events of 13 May 2005 and have called, so far in vain, for an independent inquiry.
Brussels has imposed a visa ban on some of Mr Karimov's most senior officials and has suspended certain political and trade relations, while similar measures are being drawn up in the US. But Mr Karimov, an authoritarian Soviet-era leader who has ruled Uzbekistan since 1989, has dismissed calls for an inquiry and has found strong support from Russia and China.
His version of events could not be more different from that of human rights activists. He claims the final death toll was 187 and that most of those killed were "terrorists" who were planning to overthrow the government with the help of foreign extremists and radical Islamist groups. His troops had no choice but to get tough, he argues, since they were facing a well-planned coup attempt that, if successful, would have given radical Islam a foothold in one of central Asia's most important countries.
Mr Karimov's case is helped by the fact that the Andijan events appear to have been triggered by the violent actions of disgruntled friends and relatives of 23 businessmen on trial for Islamic extremism. They attempted a jailbreak, seized weapons, killed an unknown number of security officials, and took hostages.
That then led to apparently spontaneous street protests in Andijan, where thousands of locals gathered to protest against the crushing poverty they live in. It was those crowds that found themselves fired upon without warning by heavily armed troops backed by armoured personnel carriers.
Human rights groups do not dispute that the authorities had to react firmly to the unfolding situation. But they allege that disproportionate force was used, that between 500 and 1,000 unarmed civilians were killed in the clampdown that followed, and that the government has used the massacre as a pretext for a crackdown on its enemies.
Allison Gill, the head of Human Rights Watch's Moscow office, said the EU and the US needed to impose tougher sanctions against Tashkent and complained that a year later there was still no justice for the victims of Andijan. "In the year since the Andijan massacre, there has been a stunning lack of accountability," she said.
She added that more than 150 people had been convicted in connection with the Andijan protests by the Uzbek authorities in the past year, in a series of what she called "show trials".
Kenneth Roth, the executive director of Human Rights Watch, said: "The Uzbek government has spared no effort to silence anyone who dares to speak the truth about what happened in Andijan."
This week, a small demonstration of activists demanding an independent investigation into Andijan was broken up in Tashkent. And Mr Karimov shows few signs of changing his hardline approach. Russian television showed him meeting the Russian President, Vladimir Putin, at a Black Sea resort yesterday to agree an agreement on closer co-operation between Uzbekistan and Russia. Neither of them mentioned Andijan during the talks.
Slaughter and its aftermath
* 13 MAY 2005
At least 500 killed in eastern city of Andijan when security forces fire into crowd of demonstrators protesting against the imprisonment of businessmen accused of Islamic militancy. Karimov regime denies killing anyone.
* SEPTEMBER 2005
Uzbekistan puts 15 suspects on trial. It is condemned as a 'show trial' and travesty of justice.
* NOVEMBER 2005
Supreme Court convicts the 15 men of organising the unrest and jails them for between 14 and 20 years. Human rights groups claim torture was used to extract forced confessions.
* DECEMBER 2005
58 others sentenced. The government claims the death toll was 187, and that most were killed by the 'Islamic insurgents' who organised the unrest.