KABUL, Afghanistan — Militants staged two suicide attacks that killed at least 19 people on Saturday, the first full day of U.S. Defense Secretary Chuck Hagel’s visit to Afghanistan. They were a reminder of challenges posed by insurgents to the U.S.-led NATO force as it hands over the country’s security to the Afghans.

“This attack was a message to him,” Taliban spokesman Zabiullah Mujahid said of Hagel, in an email to reporters about the bombing outside the country’s Defense Ministry in Kabul.