IEBC boss Wafula Chebukati thanked Kenyans for coming out to protest the murder. His mutilated body and that of an unidentified woman was found later on Monday. He had publicly sought to reassure voters that the results of the August 8 election would not be tampered with.
While Amnesty International's Kenya researcher Abdullahi Halakhe said the death so close to election day should be a red flag to Kenyan authorities. "We are demanding government provide security to all IEBC staff".
Mr. Msando, was in charge of the system, had reported several death threats before he was murdered.
Caro and Mr Chris Msando, had been friends for months, the sister said.
The group recently threatened to disrupt Kenya's election and has carried out more than 100 attacks inside the country since 2011 in retribution for Kenya sending troops to Somalia to fight it.
They called on the government to investigate Kuria on his possible involvement in the search of the whereabouts of Msando.
In 2013, electronic voting machines suffered widespread malfunctions, and Odinga took his complaints to court, only to have them dismissed.More news: The World's Longest Suspension Footbridge Is 1600 Feet of Pure Vertigo
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Msando had reported to police in December that he had received threatening messages and phone calls in October, the statement said, but he had not followed up his initial complaint.
The body of senior Kenyan election official Christopher Chege Msando was discovered this week on the outskirts of Nairobi, showing signs of torture, according to police.
Incumbent President Uhuru Kenyatta is locked in a tight race with Raila Odinga.
Both sides have accused the other of underhand tactics; the president says Odinga is trying to divide the nation and provoke violence, while the opposition leader claims Kenyatta plans to rig the poll.
In a statement Monday, U.S. Ambassador to Kenya Robert Godec and his British counterpart Nic Hailey said their countries are "gravely concerned by the murder" and have offered to help with the investigation.
Mass violence erupted leaving more than 1,000 people dead following Kenya's 2007 disputed presidential election.
Rashid Abdi, regional analyst at worldwide crisis group, also expressed fear that public confidence in the vote could be affected.