His life had taken him from the northern tip of Sri Lanka to a pebble-dashed semi in north-west London and finally to a cold square in Geneva. But it is for his death that the 26-year-old Tamil, Murugathasan Varnakulasingham, is likely to be remembered.

A little after eight o'clock last Thursday night, the computing graduate and part-time Sainsbury's shelf-stacker doused himself in petrol in Geneva and set light to his body outside the United Nations complex in the Place des Nations. Police officers rushed to try to save Murugathasan, who stood "burning like a torch", but he was too badly injured. A few metres away, they found a letter typed in Tamil and English explaining why he had chosen to die: "We Tamils, displaced and all over the world, loudly raised our problems and asked for help before [the] international community in your own language for three decades. But nothing happened ... So I decided to sacrifice my life ... The flames over my body will be a torch to guide you through the liberation path."

Seven Tamils - including Murugathasan - have burned themselves to death in the past month to protest about the treatment of their people by Sri Lanka's Sinhalese government. Most were in the Indian state of Tamil Nadu, but on 14 February, another British-based Tamil allegedly tried to set himself on fire outside Downing Street, but was arrested before he could do so.

The wave of suicidal demonstrations has been provoked by the Sri Lankan government's latest attempt to crush the Liberation Tamil Tigers of Eelam (LTTE). In an attempt to end the country's 30-year civil war, Colombo has dispatched 50,000 troops to the north-east of the island. However, the offensive has left 200,000 civilians trapped between the two sides, and some estimates say 40 civilians are being killed each day. Both sides stand accused of atrocities: the LTTE of using civilians as human shields and forcing people to join its ranks and the government of indiscriminate shelling and setting up internment camps for Tamils.

According to his younger brother, Velmurugan, Murugathasan had become obsessed with the suffering of the civilians and had begun to devour reports and images of what was going on in the country he left seven years ago. "He was a very emotional guy and it just made him worse. He couldn't eat and he just cried."

He added that the reports reminded his brother of the two years the family spent in a camp for displaced people in Kilinochi after the war forced them to leave their village in Jaffna. "He always worried about the people who were going through what he had gone through."

Although Murugathasan joined tens of thousands of fellow British-based Tamils on their protest march through London at the end of January, he could not shake a feeling of powerlessness. "He went to Geneva saying that he was going to participate in the protests," said Velmurugan. "He kept talking about the guys who had burnt themselves in India, saying: 'They're doing this for us. What are we doing for them?' "

But Murugathasan gave his family no hint of his intentions and they remain convinced that his suicide was a spur-of-the-moment decision. Velmurugan said: "He rang home last Monday, he sounded normal and said he would be coming back on Friday."

His brother, he added, was not a tough guy. "He was very soft. If he fell and hurt his leg, he would cry." The family learned about the death through the Tamil media and said they had had no contact with the Swiss or British authorities.

His mother, who has been inconsolable, sat weeping in the living room of the family's home in Harrow. A few feet away was a makeshift shrine with Murugathasan's picture on a table flanked by the television and stereo and surrounded by incense and flowers.

Thaya Idaikkadar, a local Labour councillor and chairman of the British Tamil Councillors and Associates, said: "He did not do this for himself or his family, he did it for his people. He was pushed into it because the media won't tell people what's going on." However, he was keen to add that Murugathasan's actions could not be condoned. "We do not support any form of suicide - our advice is that no one else should ever do what he did."

The family is now trying to plan what they think could prove to be "a small state funeral", with thousands of Tamils from all over the UK coming to pay their respects.

Velmurugan, though, is still struggling to understand what was going through his brother's mind as he stood in the Place des Nations. "Maybe he told himself: 'By losing my life I can save thousands of people.' These were the only weapons he had. He had only himself to burn."