Four people were killed and 14 others wounded in an attack at the Turkish Aerospace Industries' headquarters on Wednesday, President Tayyip Erdogan said.
Interior Minister Ali Yerlikaya said two attackers were killed in what he called a terrorist attack, adding three of the injured are in critical condition. TV broadcasters earlier showed footage of armed assailants entering the TUSAS building.
"Two terrorists were neutralized in the terror attack on the TUSAS Ankara Kahramankazan site," Yerlikaya said, referring to the Aerospace Industries.
Turkish President Tayyip Erdogan, alongside Russia's Vladimir Putin at a BRICS conference in the Russian city of Kazan, also called it a terrorist attack.
Closed circuit television footage showed an exchange of gunfire. /Handout
Erdogan told reporters: "I especially thank you for your condolences. We have four martyrs and 14 injured. I condemn this heinous terrorist attack and wish God's mercy to our martyrs."
The cause and perpetrators of the blast and subsequent gunfire remained unclear. No group had claimed responsibility. Prosecutors have launched an investigation, state-run Anadolu Agency reported.
Some media reports claimed a suicide attack had occurred and that there were hostages inside the building, though officials have not confirmed this.
Witnesses told Reuters that employees inside the building were taken by authorities to shelters and no one was permitted to leave for a few hours. They said the blasts they heard may have taken place at different exits as employees were leaving work for the day.
Broadcasters showed images of a damaged gate and footage of an exchange of gunfire in a parking lot, as well as attackers carrying assault rifles and backpacks as they entered the building. Ambulances and helicopters later arrived.
TUSAS is Türkiye's largest aerospace manufacturer, currently producing a training craft, combat and civilian helicopters, as well as developing the country's first indigenous fighter jet, KAAN. Owned by the Turkish Armed Forces Foundation and government, it employs more than 10,000 people.
NATO Secretary General Mark Rutte condemned the attack and said the military alliance would stand with its ally Türkiye. The European Union delegation in Türkiye also condemned the attack.