Tuesday's attack in Kabul killed at least 37. Separately, an attack in Kandahar killed 13, including five United Arab Emirates officials.
Afghan security officials began investigating Tuesday's attacks in the capital Kabul and the southern city of Kandahar as the death toll climbed to at least 50.
Authorities said at least 37 died in the Kabul attack, with 98 wounded. Thirteen people were confirmed dead in Kandahar.
The Taliban claimed responsibility for the suicide and car bomb attack in the Afghan capital. They denied responsibility for the attack in Kandahar which killed mainly government officials or diplomats from the United Arab Emirates who were visiting the city to open an orphanage. Thirteen people were confirmed dead in Kandahar.
On the same day as the two attacks, seven people were killed in a Taliban attack on a security unit in the southern province of Helmand.
Thousands of civilians have been killed in Afghanistan in the 15 years since the Taliban government was brought down in the US-led campaign of 2001.
In July, the UN Assistance Mission in Afghanistan reported that 1,601 civilians had been killed in the first half of the year, a record since it began collating figures in 2009.