Gunmen have killed two aides of an Afghan presidential candidate, hours before the official election campaign was due to start.
The attack on Saturday targeted staff working for Abdullah Abdullah.
Abdul Rauf Ahmadi, a police spokesman in Herat, said: "Two people, Ahmad Hamdard and Shujahideen were killed in the fourth district of Herat. Unidentified gunmen opened fire on them in the middle of street."
Sayed Fazel Sangcharaki, a spokesman for Abdullah, said Hamdard who was to lead the candidate's election campaign team in Herat.
The attack came as the country prepares for the democratic transfer of power, with the April 5 electionviewed as a test for Afghan security forces.
Taliban fighters have threatened to target the campaign, and the Afghan police and army face a major challenge as the US-led NATO troops prepare to exit.
No one has yet said they carried out the attack.
Campaign kicks off
But a source close to Abdullah, who did not wish to be named, told the news agency AFP: "We had received some threats in the past week, and two suspects were detained three days ago near our election campaign office in the city.
"We had also informed the security forces that there may be more possible threats, but unfortunately despite some security measures taken by us and police there, two main members of our election team were killed this evening."
The source did not elaborate on who was behind the threats.
Sangcharaki, who said Hamdard had worked with Abdullah during the last presidential campaign in 2009, criticised the lack of security provided by the government.
"This incident at the beginning of election campaign is a bad sign as either the security forces are incapable of providing security for the election campaign or they do not take their job seriously," he said.
Abdullah came second to President Hamid Karzai in the 2009 election.
Afghanistan's election campaign kicks off on Sunday, with 11 candidates vying to succeed Karzai as the country enters an uncertain new era without the aid of NATO combat troops to fight the Taliban.
A dispute between Kabul and Washington over whether a small force of US soldiers stays behind beyond 2014 is likely to dominate the two-month campaign.