"A young military man working in Afghanistan told me that elections in Afghanistan are ... much better run than the USA’s 2020 Election," the president tweeted.
No one immediately claimed responsibility for the attack in Kabul.
The international press freedom group Reporters Without Borders has called Afghanistan one of the world’s deadliest countries for journalists.
Some members of Congress, including Republicans, have argued that the U.S. troop reduction is unwise or premature.
Gunmen stormed Kabul University as it hosted a book fair attended by the Iranian ambassador to Afghanistan.
Trump's ambassador pick wants to pull the U.S. out of Afghanistan. The failure to confirm him shows how far Republicans are from being anti-war.
"God bless Boeing," the president said in 2017, a year that saw him approve nearly twice as many arms deals as Barack Obama did in his final year in office.
The president who dropped the world's largest non-nuclear bomb is using surreal '60s-style imagery and the message "Make Peace Not War" in new ads.
President Donald Trump is under fire after a new report claimed that Russia offered Afghan militants a bounty for killing American troops.
An explosive report claims Trump knew a Russian military unit was paying Afghan militants a bounty to kill U.S. soldiers.