Sumi Khan has been in the UK (1 March) to collect an Index on Censorship award for "outstanding commitment to journalistic integrity in defence of freedom of expression".

The letter to Sumi Khan told her to immediately retract all the articles that she had written on Islamist groups, and threatened grenade attacks on her home and office if she ever reported on these issues again.

All three are reporters for publications based in the city of Chittagong, in the south of the country. Samaresh Baidya works for the daily newspaper Bhorerkagoj; Zubair Siddiqui works for a weekly magazine, Ajker Surjodoy; and Sumi Khan writes for the magazine Shaptahik 2000.

Sumi Khan had received previous death threats after writing investigative articles alleging the involvement of local politicians and religious groups in attacks on members of minority communities, and about kidnapping and land grabbing by landlords. She was stabbed and critically wounded on 27 April 2004.

Three men in an auto-rickshaw attempted to drag her into their vehicle, but she resisted. They then stabbed her several times.

Before the attack, she received several threatening telephone calls, warning her not to defame people in her reports. The people who came to Sumi’s rescue heard the assailants yelling about her reports in the paper, saying she would be killed if she did not stop writing.

The death threats and attack are believed to be linked to her articles. She received more threatening phone calls as she recuperated at home. Sumi has filed a complaint with the police about the attack, but so far no-one has been arrested.

Amnesty International UK Individuals At Risk Programme Manager, James Savage, said:

"Sumi, Samaresh and Zubair are in grave danger. It’s important that here in the UK we stand up for them. Amnesty members are calling on the Bangladeshi authorities to do more to protect those who speak out and bring to justice those responsible for such threats.

"Human rights defenders in Bangladesh are frequently at risk of attack and yet prosecutions of those who threaten and attack them are rare. And the problem goes far wider than Bangladesh. All over the world, journalists, lawyers and activists are right now standing up for human rights in the face of threats and violence."

At least four journalists have been killed in the past year in Bangladesh and dozens have been threatened or seriously injured in violent attacks. These attacks and threats relate directly to the issues that journalists have been reporting on.

No one has been brought to justice for these threats and attacks, and many journalists and human rights defenders live in a constant state of intimidation, unable to carry out their work without fear of attack.

Amnesty International warned that many more human rights defenders – journalists, lawyers and activists – face threats and attacks every day around the world.

Already this year, Amnesty International has issued urgent appeals for 17 human rights defenders at grave, immediate risk in Bolivia, China, Colombia, Guatemala, Honduras, Iran, Mexico, Nepal, Russia, Sudan and Turkey.