Afghan police have detained nine senior employees of a private security company that provided guards to the Kabul hotel attacked by the Taliban last week.
The interior ministry said in a statement on Tuesday that the company employed by the Serena Hotel was negligent, which enabled the four attackers to hide small handguns in their shoes and avoid detection to enter the premises.
The gunmen opened fire inside the hotel restaurant, killing nine people, including two children and four foreigners. Police killed the attackers.
The ministry did not identify those detained. Afghanistan earlier accused Pakistan's intelligence service of orchestrating the attack but Islamabad denied involvement.
The nine were detained as an explosion and gunfire rattled the house of Afghan presidential candidate Ashraf Ghani, a senior police officer said, adding Ghani was not home at the time.
"Four people entered Ashraf Ghani's house and there was an explosion followed by gunfire," the officer told Reuters.
There were no immediate reports of casualties. Ghani is a former World Bank official who has picked powerful former Uzbek warlord Abdul Rashid Dostum as his running mate.
The attack on the luxury lodging last week left nine people dead and authorities seemed stunned that the fighters had managed to get through tight security at the Serena Hotel — considered one of the safest places to stay in Kabul.
Among the dead was Sardar Ahmad, 40, an Afghan journalist for Agence France-Presse, killed along with his wife and two of his children, the French news agency confirmed. In response, an association of reporters in the country, the Afghan Journalist Family, imposed a 15-day boycott of Taliban-related coverage.
The attacks show the Taliban are following through on their threat to use violence to disrupt the April 5 elections. The presidential vote will be the first democratic transfer of power since the 2001 U.S.-led invasion that ousted the Islamic militant movement. President Hamid Karzai is constitutionally barred from seeking a third term.
Al Jazeera and wire services