Unknown gunmen shot dead two aides of Afghan presidential candidate Abdullah Abdullah late on Saturday in the western city of Herat, highlighting concerns about security in the run-up to the April vote.
Shujahudeen and Dr Faiz Ahmad Hamdard were shot dead on Saturday around 06:30 pm by unknown gun men driving a car, officials said, while they were finishing campaigning for Abdullah, officials said.
"It's our rivals who are behind it," said Fazl Rahman Orya, a spokesman for Abdullah Abdullah, who declined to name anyone.
"No one coordinated with us regarding Dr Abdullah's electoral campaign and about their office. And regarding whether they were Dr Abdullah's electoral campaign aides or not, we cannot confirm that because till yet electoral campaigning are not started officially and there were no coordinating information with police from before," said Samiullah Qatra, Provincial Police Chief.
The killing occurred just one day before the official start of the election campaign.
Security officials in Herat province say no one has yet claimed responsibility for the attack, and the police have started investigations.
Taliban insurgents have threatened to target the candidates.
The Special Representative of the United Nations Secretary-General for Afghanistan, Ján Kubiš in a statement on Sunday has "strongly condemns the killing of the two members of the election campaign team of one of the presidential candidates, Dr. Abdullah Abdullah. They were shot dead by unidentified gunmen in Herat city on Saturday night."
"The Special Representative sends his deepest condolences to the families, friends and colleagues of those who lost their lives in this criminal act," the statement said.
"The attack came at a critical moment for Afghanistan on the eve of the election campaign as the country prepares for the presidential and provincial polling in April. This coward action constitutes a violent intimidation of electoral candidates and their supporters, and cannot be tolerated," it added.
Security has been a top concern for Afghan officials leading into this year's elections, which come as President Hamid Karzai leaves office and the NATO coalition leaves Afghanistan.
A number of presidential candidates have mounted criticisms recently against what they say are insufficient security measures being taken to protect the elections.
The election campaigns to begin on February 2, but many in the public fear insecurity issues in certain parts of the country could prove too much for the elections all together.
