Nairobi - Kenya's president said Tuesday he is "deeply shocked" by the torture and killing of an election official who was crucial to next week's presidential vote, while concerns grew that the election again will face dangerous unrest.President Uhuru Kenyatta said on Twitter that investigations into Christopher Msando's killing should be allowed to "proceed calmly," and he warned against "careless speculation."Msando was in charge of managing information technology systems at the electoral commission. He had publicly sought to reassure voters that the results of the August 8 election would not be tampered with.Analysts have warned that further violence could accompany the hotly contested election in which Kenyatta is running again. The country's elections have turned violent in the past, notably after the 2007 vote that international observers said was flawed. More than 1 000 people died.The main opposition group has charged that Kenyatta wants to rig the upcoming election, an accusation the presidency has denied. The National Super Alliance called Msando's death an assassination and an attempt to disrupt the vote.The US and British diplomats in Kenya have expressed grave concern about Msando's death and offered the Kenyan government assistance in investigating.Hundreds of activists on Tuesday marched peacefully to the electoral commission to protest the killing. A former government official turned whistleblower, John Githongo, said there was plenty of reason to believe Msando's death was related to the election.The electoral commission chairperson, Wafula Chebukati, has called the death a "brutal murder" and called for security for all commission staff."Let us remember Chris by voting peacefully," Chebukati told Tuesday's gathering. The commission "shall ensure that the ground for voting on the eighth of August is level for everyone. So we can remember Chris best by participating in free, fair and credible elections."Kenya's police chief Joseph Boinnet has said a special team from the Directorate of Criminal investigations has been set up to investigate Msando's murder.