The U.S. also has deployed more military resources to Afghanistan in the first quarter of this year, Mr. Sopko reported, shifting more warplanes from Iraq and Syria to Afghanistan and moving the first U.S. Army Security Force Assistance Brigade to the country to increase training capacity of Afghan forces.
It also comes on the heels of another deadly day in the capital, when twin blasts killed at least 25 people, including Agence France-Presse chief photographer for Afghanistan Shah Marai and eight other journalists.
"I don't know what I will do in the future but I don't want to be killed for my work".
The statement from IS's "Khorasan" province, the group's Afghan branch, said a first attacker "struck the headquarters of the Afghan intelligence services in Kabul". Press secretary Sarah Huckabee Sanders said there was "absolutely no justification for such a senseless and heinous act".
"We'll stand by the Afghan people, we'll stand by the Afghan government and the North Atlantic Treaty Organisation mission will continue as we drive them to a political settlement", he added.
The murder of journalists and other innocent people was a great testimony to what the U.S. stood for, and more importantly, what it stood against, the secretary remarked.
At the same time, the Taliban and other insurgent groups now control or influence 14.5 percent of Afghanistan's 407 districts - the highest level since SIGAR started recording such data in late 2015.
SIGAR added that the size of the Afghan security forces has sharply declined over the past year.
But following the recent bombings - as well as a new audit showing that Afghan security forces have shrunk by 10 percent - Mattis stressed that work is still ongoing to improve the situation within the country.
He said attacks which target press freedom and democratic values will further strengthen the resolve of the European Union to stay alongside the people of Afghanistan.
The head US commander in Afghanistan, Army Gen. John Nicholson, later said that he agreed with Ghani's assessment.
At the start of March, about 7,800 US special forces were in the country to train, advise, and assist Afghan troop, according to SIGAR.
"So the expansion there is why the enemy has been unable to take any district centers provincial centers or make any advances there", Mattis said in response to a question. It also said that the insurgents gained control over a larger portion of the population - from 9 percent in August 2016 to 12 percent in January.