"We recognize and appreciate that the Government of Bangladesh has arrested eight individuals and is seeking justice in the Kibria assassination case. We urge you to do all you can to see that the investigation is conducted in a fair, expedient and transparent manner and meets international standards," four US senators and eight congressmen said in a letter addressed to Rice on June 23.

"It is important that this investigation restores public confidence in the justice system, and that is viewed as valid and legitimate by wide and diverse segments of Bangladeshi Society. A delegation of international observers could advance this goal," the letter says.

"If the investigation does not bring to justice the perpetrators of Mr. Kibria's murder, including those who organized and ordered the attack and any who may have worked to protect the perpetrators, then we urge you to propose a resolution in the United Nations Security Council calling for an independent, international investigation, which would send a clear signal that the international community will not tolerate a climate in which political violence flourishes," the letter reads.

The senators and congressmen noted that recent acts of political violence in Bangladesh, including the assassination of Kibria in January this year and the attempts on the life of British high commissioner in May, 2004, and on Awami League leader Sheikh Hasina Wazed in August, 2004, continue to be unsolved.

The co-writers of the letter to Rice include, US senators Edward M Kennedy, John F Kerry, John Sununu, and Lincoln D Chafee, and US congressmen Barney Frank, John W Olver, Richard E Neal, James P McGovern, John F Tierney, Edward J Markey, Michael E Capuano and Charles F Bass.