The casualty total from Tuesday's major attack in Kabul has risen to 64 killed, more than double the total previously estimated by police, and 347 wounded, Afghan Interior Ministry spokesman Sediq Sediqqi says.
He said on Wednesday most of those killed in the attack, which hit a security services office in the heart of the government and diplomatic area of the Afghan capital, were civilians.
The attack, which was quickly claimed by the Taliban, was the deadliest single incident of its kind in Kabul since 2011 and came only days after the Islamist insurgent movement announced the start of its annual spring offensive.
It began at around 9am (1530 AEST), in the middle of the morning rush hour, when a suicide bomber in a vehicle packed with explosives blew himself up in front of an office of a department of the National Security Directorate.
In a pattern similar to major attacks in Kabul and other Afghan cities, the bombing was followed by one or more gunmen who engaged in an extended shootout with security forces.
The attack underlined concerns raised in a United Nations report this week, which said an increase in urban warfare had caused a spike in civilian casualties during the first three months of the year.
