Four people were killed and 14 others wounded in an attack on the headquarters of a top Turkish defence firm near Ankara, Turkish officials said yesterday.

President Recep Tayyip Erdogan, who was holding talks in Russia with Vladimir Putin at the time, confirmed the toll, and condemned what he said was a "heinous terrorist attack" at state-run Turkish Aerospace Industries (TAI).

Interior Minister Ali Yerlikaya said three of the injured were in critical condition and that two attackers "a woman and a man, have been neutralised".

He said work was under way to determine their identities but did not say whether there were any other attackers still at large.

Local media broadcast footage showing clouds of smoke and a large fire raging at the site in Kahramankazan, a small town some 40 kilometres (25 miles) north of Ankara.

The incident happened as Erdogan was meeting Vladimir Putin at a summit in Kazan, with the Russian leader expressing his condolences over the attack.

Media outlets which had been showing live footage from the scene were forced to halt their broadcasts after Turkey's media watchdog ordered a blackout of images from the site.

Haberturk TV said there was an ongoing "hostage situation" without giving further details, while the private NTV television spoke of gunshots after the blast, which took place around 4:00 pm (1300 GMT).

There was no immediate claim for the attack but the justice minister said an investigation had been opened.

NTV spoke of a suicide attack, saying "a group of terrorists" had burst into TAI's headquarters and one of them blew themself up.

Images shown by Haberturk suggested one attacker was a woman, while Sabah newspaper published a CCTV image from cameras at the building's entrance of a black-clad young man with a moustache carrying a rucksack and what appeared to be an assault rifle.