KABUL, Afghanistan (AP) — U.S. Defense Secretary James Mattis arrived on a surprise visit to Afghanistan’s war-shattered capital on Friday, the U.S. command in Afghanistan said, just days after a suicide bomber killed 21 people in the city and wounded 90 others.

As helicopters patrolled the skies over Kabul, Mattis arrived accompanied by Gen. Joseph Dunford, chairman of the joint chiefs of staff. He was expected to meet President Ashraf Ghani, presidential spokesman Mohammad Haroon Chakhansuri told The Associated Press. He was also expected to meet Afghan, U.S. and NATO military commanders.

Mattis’ arrival comes amid brutal assaults against the country’s minority Shiites and a fresh round of insider attacks this week that have claimed the life of one American service member and eight local police.

While in Kabul, Mattis is expected to discuss the escalating violence against both civilians and military personnel.

The U.S. has been supporting Afghan forces in an aggressive campaign against Islamic State group insurgents in eastern Nangarhar province, yet the IS affiliate has repeatedly been able to carry out horrific and brazen attacks in the heavily fortified capital of Kabul.

The victims have most often been Afghanistan’s minority Shiite Muslims. The radical Sunni Islamic state reviles Shiites as apostates.