Interior minister Ali Yerlikaya said the two attackers - a man and a woman - were killed after the alleged terror incident at a defence and aerospace company in the capital.

Two of the 22 injured were said to be in critical condition.

Turkey attack catch up: Updates as it happened

In response, Turkey conducted two days of strikes in northern Syria and northern Iraq.

While no one has claimed responsibility yet, the Turkish defence ministry said its jets conducted airstrikes in both countries against Kurdistan Workers' Party (PKK) targets.

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

The country's National Intelligence Organization added that it had targeted numerous "strategic locations" used by not just PKK, but also Syrian Kurdish militia affiliated with the group, according to the state-run Anadolu Agency.

Targets were said to include military, intelligence, energy, and infrastructure facilities and ammunition depots, it was reported.

A security official said armed drones were used in Thursday's strikes.

On Wednesday, Turkey's air force carried out airstrikes against similar targets in northern Syria and northern Iraq hours after the initial incident.

Defence minister Yasar Guler said that Wednesday's airstrikes destroyed 47 alleged PKK targets - 29 in Iraq and 18 in Syria.

In Syria, the main US-backed force said that Turkish strikes had killed 12 civilians and injured 25 people.

The Kurdish-led Syrian Democratic Forces claimed the attacks hit bakeries, power stations, oil facilities and local checkpoints.

'Heinous terrorist attack'

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

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

CCTV captured two gunmen, the man and the woman, entering the facility with assault rifles and backpacks.

Turkey's state-run news agency named the five victims, and their occupations: quality control employee Cengiz Coskun; mechanical engineer Zahide Guclu; employee Hasan Huseyin Canbaz; security personnel Atakan Sahin Erdogan, and taxi driver Murat Arslan.

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

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

How the attack unfolded

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

Carrying assault weapons, they detonated an explosive device next to the taxi, causing panic and allowing them to enter.

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

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

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.

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'We stand with Turkey'

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 also condemned the attack and said that the bloc stood with Turkey.

The attack came a day after Mr Erdogan raised the possibility that PKK's imprisoned leader could be granted parole if he renounces violence and disbands his organisation.

There was no immediate statement from the PKK on the attack or the Turkish airstrikes.