Turkey has pointed the finger of blame at PKK, which has been waging an armed rebellion against Ankara for decades.

Within hours of the attack, Turkey carried out air raids on northern Iraq, targeting what it said were 20 PKK positions. Ankara has long claimed that the PKK is sheltering across the border in Iraq’s Kurdish province.

The PKK has been designated as a “terrorist organisation” by Ankara and its NATO allies, who condemned Sunday’s attack as “terrorism”.

So, what’s the story behind this attack?

What exactly happened in Ankara?

On Sunday, a car with two men inside pulled up at the Interior Ministry’s gate in the Kizilay neighbourhood of the Turkish capital.

Security camera footage showed the attackers getting out of the car and the person in the passenger seat rushing towards the gate with what appeared to be an assault rifle or rocket launcher before being engulfed in an explosion. Then, the second person started shooting.

Turkish authorities said the first perpetrator was killed when he detonated the bomb on his person, and the second attacker was shot dead. Two police officers were slightly injured.

The attackers are believed to have started their operation in Kayseri, 260km (161 miles) southeast of Ankara where they are suspected of killing a veterinarian and taking his vehicle to avoid arousing suspicion in Ankara, according to local media reports.

An RPO-A Shmel Russian-made rocket launcher was found at the scene, according to reports.

The timing of the attack

A statement attributed to the PKK, claiming it was behind the blast, was released by pro-Kurdish news agency ANF

It said a team affiliated with the Kurdish armed group’s “Brigade of Immortals” was behind the attack, which was “an act of legitimate defence” against the Turkish government, which the statement accused of trampling on the rights of the Kurdish people.

The statement carried by ANF went on to say that the timing and placement of the attack was intended to come shortly before the opening of Parliament after the summer recess.

Among other things, the Turkish parliament is expected to discuss ratifying Sweden’s accession to NATO soon. NATO member Turkey has demanded that Sweden crack down on “Kurdish separatists” in its territory as a condition for its ratification.

The statement claimed the attack was successful and achieved its goal, even though the perpetrators failed to pass the ministry’s gate.

The fact that the attack took place at about 9:30am (06:30 GMT) on a Sunday when streets were nearly empty hints civilians might not have been the targets.

What has the investigation found out about the suicide bombing?

So far, Turkish intelligence and security apparatuses have been staging raids across the country.

After raiding 28 addresses, they have arrested 20 individuals with links to the suicide bombing, including a few politicians from the pro-Kurdish HDP party, according to Al Jazeera’s Sinem Koseoglu reporting from Turkey. The politicians have been accused of fundraising for PKK elements outside the country.

In addition, Koseoglu said, Turkish intelligence claims to have “neutralised” the mastermind of a 2007 attack in Daglica that killed 12 Turkish soldiers.

Muzdelif Taskin was “neutralised” in northern Syria, in the city of Qamishli, Turkish news agency Anadolu said.

Why does Turkey want to stamp out the PKK?

The PKK is designated a “terrorist organisation” by Turkey, the European Union and the United States.

Initially taking up arms against the Turkish state in 1984, the PKK has waged a rebellion that resulted in the death of tens of thousands of people.

Its stated goal is the creation of an independent socialist Kurdish state in the territory of “Kurdistan” in southeast Turkey.

The PKK and its offshoots have carried out numerous attacks on military and security forces as well as civilians in Turkey.

Turkey regularly conducts military operations in southeastern parts of the country with the aim of forcing the PKK out. It has also cracked down on Kurdish politicians, journalists and activists in the country.

Ankara has also been regularly targeting PKK positions in northern Iraq, drawing anger from Baghdad, which accuses Turkey of violating its sovereignty.