Interior minister Ali Yerlikaya said the two attackers - a man and a woman - were killed. Two of the 22 injured are in critical condition.

Multiple gunshots were heard after Turkish security forces entered the site, in the capital city of Ankara, local media reported.

"I condemn this heinous terrorist attack and wish mercy on our martyrs," President Recep Tayyip Erdogan said during a meeting with Russian President Vladimir Putin on the sidelines of a meeting in Kazan, Russia.

Turkey attack latest: Follow live updates

Mr Putin, who is hosting world leaders at a summit of the BRICS bloc of developing economies, expressed his condolences.

One of the victims was identified as mechanical engineer Zahide Guclu, who had gone to the entrance to collect flowers sent by her husband, the state-run Anadolu Agency said.

Mr Yerlikaya said the militant Kurdistan Workers' Party, or PKK, was believed to be behind the attack at the defence company. Defence minister Yasar Guler also accused the PKK.

While no one has claimed responsibility yet, the Turkish defence ministry said its jets have conducted airstrikes in northern Iraq and northern Syria against PKK targets in response to the attack.

PKK is considered a terrorist group by Turkey and its Western allies.

In total, 32 targets were struck and aerial operations were continuing, the ministry said.

Kurdish militants, the Islamic State group and leftist extremists have all carried out attacks in the country in the past.

TUSAS (Turkish Aerospace Industries) is one of Turkey's most important defence and aerospace companies and produces KAAN, the country's first national combat aircraft, among other projects.

Turkish media said the assailants arrived at an entry to the TUSAS complex in a taxi.

The assailants, carrying assault weapons, detonated an explosive device next to the taxi, causing panic and allowing them to enter.

The taxi driver was also killed by the assailants and his body was found in the trunk of the vehicle, Anadolu agency reported.

CCTV images from the attack appeared to show a man in plain clothes carrying a backpack and holding an assault rifle.

Videos circulating on social media show residents ducking for cover as large explosions were heard during the attack today, followed by what seemed to be gunfire.

Multiple gunshots were heard after security forces entered the site, the DHA news agency and other media reported.

Helicopters were seen flying above the premises.

One video, filmed from a car park, shows people looking on as dust filled the air a short distance away as more gunfire was heard.

Security forces, ambulances and firefighters were all said to have been dispatched to the site.

Employees were taken to a safe area, HaberTurk television said.

Prime Minister Sir Keir Starmer said: "I am appalled by the terrorist attack in Ankara.

"We stand shoulder to shoulder with Turkey as a NATO ally and close friend.

"Our thoughts are with the families of victims and all those affected."

NATO general secretary Mark Rutte said: "Deeply concerning reports of dead and wounded in Ankara.

"NATO stands with our ally Turkey.

"We strongly condemn terrorism in all its forms and are monitoring developments closely."

TUSAS designs, manufactures and assembles civilian and military aircraft, unmanned aerial vehicles and other defence industry and space systems.