By Tuvan Gumrukcu

ANKARA (Reuters) -Turkish forces have killed 58 Kurdish militants in northern Syria in overnight attacks on militant targets, the Defence Ministry said on Saturday, as conflict in the region escalated nearly a week after a bomb attack in Ankara.

Turkey this week said all targets belonging to the outlawed Kurdistan Workers Party (PKK) militia and the Syrian Kurdish YPG militia were "legitimate targets" for its forces, after the PKK claimed responsibility for Sunday's bombing in Ankara which wounded two police officers and killed the two attackers.

Turkey said the attackers came from Syria. The U.S.-backed Syrian Democratic Forces (SDF) - a coalition of rebel groups spearheaded by the YPG militia - denied this.

Since the bomb attack, Ankara has launched a barrage of air strikes and ground-based attacks against militant targets in northern Syria and Iraq, while ramping up security operations at home.

"Targets belonging to PKK/YPG terrorists in northern Syria's Euphrates Shield, Olive Branch, and Peace Spring operation areas were hit strongly all night long," the ministry said, referring to regions where Turkey has previously mounted incursions.

The ministry said the operations, which it says are carried out under self-defence rights, had "neutralised" 58 militants in the region. Ankara typically uses the term "neutralised" to mean killed.

Late on Friday, the ministry had said Turkey's military had conducted air strikes in northern Syria, destroying 15 militant targets where it said militants were believed to be.

Interior Minister Ali Yerlikaya said on Saturday that police in the eastern province of Van had captured six people suspected of PKK links and in preparation of an attack. Following the bomb attack, authorities have carried out raids and operations across the country, seizing dozens of people.

Speaking at his ruling AK Party's congress in Ankara on Saturday, President Tayyip Erdogan repeated his warning that Turkey "may suddenly come one night", a term he has often used to target militants in Syria and Iraq.

"We will implement our strategy of ending terror at its root with determination, and hold the PKK, FETO, and Daesh to account over every drop of blood they have spilled," he said referring to the network of U.S.-based cleric Fethullah Gulen whom Ankara accuses of orchestrating a failed coup attempt in 2016 (FETO), and the Islamic State.

Turkey lists the YPG as a terrorist organisation and says it is indistinguishable from the PKK, which has fought an insurgency against the Turkish state since 1984 in which more than 40,000 people have been killed.

The United States and European Union deem the PKK a terrorist organisation, but not the YPG.

The YPG is at the heart of the SDF forces in the U.S.-led coalition against Islamic State militants. U.S. support for them has long caused tension with Turkey.

Underscoring the tension, the United States on Thursday shot down an armed Turkish drone that was operating near its troops in Syria, the first time Washington has brought down an aircraft of NATO ally Turkey.

Ankara and Washington held a series of calls following the incident, with Turkey saying non-conflict mechanisms with the parties on the ground would be improved, but vowing to continue hitting militants in Syria and Iraq.

Turkey, which has mounted several incursions into northern Syria against the YPG, has said a ground operation into Syria is an option it could consider.

Turkey says it killed 58 Kurdish militants in northern Syria