The attack came just three days after more than 140 Afghan soldiers were killed in an attack on their base by Taliban fighters disguised in military uniforms.
Afghanistan's President Ashraf Ghani (R) arrives to visit the victims of April 21's attack on an army headquarters, in Mazar-i-Sharif, northern Afghanistan April 22, 2017. Mr. Mattis was also supposed to speak with General Habibi, the defense minister, but it was unclear whether his resignation had changed those plans. The Taliban are using the weapons in the southern provinces of Helmand, Kandahar and Uruzgan, according to the official, who briefed journalists on intelligence information on condition of anonymity.
Mattis was expected to meet U.S. troops stationed in the war-torn country and Afghan officials.
The Taliban claimed responsibility for the attack and said it was in retaliation for the recent killings of Taliban shadow governors for Kunduz and Baghlan provinces.
The US State Department on Monday described last week's Taliban attack in northern Afghanistan as "unconscionable", but stressed America has no intention of giving up on the country despite more than 15 years of brutal war.
The official said it appears likely the attack was either carried out by or planned by a Pakistan-based Taliban faction known as the Haqqani network, which is a USA government-designated terrorist organization.
The attack underlines the scale of the challenge facing the Western-backed government and its worldwide partners more than 15 years after the United States invaded the country.
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Forty-eight hours after the attack, the president's office and the defence ministry put the number of dead and injured at "more than 100".
In the Taliban's detailed statement on the attack, posted on the militant group's website, spokesman Zabihullah Mujahid said that four of the 10 attackers were disguised as soldiers.
Mattis's arrival coincided with the announcement of two high-profile Afghan resignations. 'Our enemy sensed that and they have redoubled their efforts, and it's time for us, alongside our Afghan partners, to respond'. It remains the deadliest attack on the spy agency during the Afghan war.
Shortly after the Pentagon chief arrived in Afghanistan, a bomb attack hit near an airfield used by the USA military in the eastern province of Khost.
"The numbers of the Afghan security forces are decreasing, while both casualties and the number of districts under insurgent control or influence are increasing", the report stated.
Ten militants first targeted a mosque inside the base where army staff were performing Friday prayers, before moving on to a dining facility.