Despite a spate of bloody incidents that made global headlines, the total number of deaths in terrorist attacks fell last year by 14 percent, a US government report said Thursday, while it refrained from referring to the PYD and YPG as terrorist organizations.

While the Daesh terrorist group remains the major threat and carried out devastating attacks in France, Lebanon and Turkey -- violence and total deaths decreased in Pakistan, Iraq and Nigeria.

The U.S. again refrained from labeling the PYD and its armed wing, the YPG, as terrorist organizations in a report released Thursday.

In its annual country account on terrorism, the State Department noted that Ankara "considers the Syria-based Democratic Union Party [PYD] and its military wing, The People's Protection Units [YPG], to be terrorist organizations," but did not follow suit.

Turkey considers the groups to be affiliated with the PKK and labels them as terrorist organizations.

While the U.S. and EU also designate the PKK as a terrorist group, Washington has refrained from labeling the PYD and YPG similarly.

The terrorist YPG group has been central to Washington's anti-Daesh strategy, and U.S. officials have called the group an "effective partner" in the campaign.

Thursday's report notes that the PKK is "prominent" among terror groups operating in Turkey and says that activity by the DHKP/C, an extreme leftist terror group, "threatened the security of both U.S. and Turkish interests" in 2015.

"So too did the actions of the Kurdistan Freedom Falcons/Hawks (TAK)," the report says.

The group claimed responsibility for the Feb. 17 and March 13 Ankara bombings that killed scores of victims in the capital.

"Turkey is a long-standing counterterrorism partner of the United States," said the report. "It continued to receive U.S. assistance to address the terrorist threat posed by the PKK in 2015."

The report said "Turkey has voiced increasing concern about terrorist groups near its border", including Daesh and al-Qaeda's Syria affiliate, the Nusra Front.

According to figures compiled for the US State Department, there were an average of 981 "terrorist attacks" per month worldwide in 2015, killing a total of 28,328 over the year.

This represents 13 percent fewer attacks and 14 percent fewer deaths than in 2014, according to the National Consortium for the Study of Terrorism and Responses to Terrorism (START).

The START figures were released Thursday as an annex to the State Department's annual strategic assessment -- "Country Reports on Terrorism" -- prepared for the US Congress.

This warned that the "global terrorist threat continued to evolve rapidly in 2015, becoming increasingly decentralized and diffuse."

The report also placed some of the blame on nation states, warning that terrorists exploit frustrations "where avenues for free and peaceful expression of opinion were blocked."

Where countries, including US allies, have rigged judicial systems and abuses by security forces and corrupt politicians go unchecked, violent non-state actors can win support.

But the single greatest threat remains the Daesh terrorist group and its growing legions of affiliates and supporters in the Middle East, Africa and South Asia.

The group has begun to lose ground to US-backed forces in its self-declared "caliphate" in Syria and Iraq, and it has begun to struggle to find funds, the report concludes.

But the Daesh group has expanded its territory in Libya, and its branch in Egypt's Sinai peninsula has gained strength, attacking local security forces and claiming the bombing of a Russian airliner.

The group has a small toehold in Afghanistan and in 2015 ordered or inspired attacks "by individuals or small groups of self-radicalized individuals in several cities around the world."

The Nigerian-based group Boko Haram pledged loyalty to Daesh in 2015, but has since come under increased military pressure from regional government forces.

Meanwhile, the Daesh group's predecessor as public enemy number one, Al-Qaeda, is seeking to mount a comeback and continues to inspire or order attacks, particularly in Yemen and East Africa.