ISTANBUL - Turkey declared a national day of mourning and began to bury its dead Sunday after twin blasts in Istanbul killed 38 people and wounded 155 others near a soccer stadium on Saturday night. It was the latest large-scale assault to traumatize a nation confronting an array of security threats.

A splinter group of the outlawed Kurdistan Workers' Party claimed responsibility for the double bomb attack.

The Kurdistan Freedom Falcons said in a statement Sunday that the two attacks were timed to go off simultaneously near the Vodafone arena, home ground of Besiktas football club, which had just concluded a match.

A relative is comforted by an army commander as family members attend funeral prayers for police officer Mehmet Zengin, 20, who was killed with dozens others late Saturday outside the Besiktas football club stadium Vodafone Arena in Istanbul, in Ankara, Turkey, Monday, Dec. 12, 2016. (AP Photo/Burhan Ozbilici) (AP)

The group said two of their members died in the attacks, but they did not specify if both were suicide attackers. The Turkish government said one of the explosions was from a car bomb, while the other was a suicide attack.

Soylu said 10 people have been detained in connection with the blasts on Saturday.

Political fallout

The Freedom Falcons said they carried out the attack to protest the imprisonment of Kurdistan Workers' Party Abdullah Ocalan and the Turkish government's ongoing military operation in the mainly Kurdish southeast of the country. "Nobody should expect to lead a peaceful life in Turkey" as long as these situations persist, the statement said.

Turkish President Recep Tayyip Erdogan said Sunday that the attackers would pay "a yet higher price" for their actions.

Turkey's pro-Kurdish People's Democratic Party condemned the attacks.

"These two bomb attacks in Istanbul have once again brought sorrow to many homes in Istanbul. We are very sad and we share the pain," the party said in a statement calling for an end to "polarizing politics" in Turkey.

Erdogan vowed that Turkey would overcome terrorism while Prime Minister Binali Yildirim ordered flags to fly at half-staff Sunday across the country and at Turkey's foreign missions.

"We have once again witnessed tonight in Istanbul the ugly face of terror, which tramples on every value and decency," Erdogan said.

In this photo taken late Saturday, Dec. 10, 2016, police forensic officers work after explosions near the Besiktas football club stadium Vodafone Arena in Istanbul. (Goktay Koraltan/Depo Photos via AP) ) (AP)

Attack details

The first and larger explosion took place about 7:30 p.m. Saturday after the home team Besiktas beat visitor Bursaspor 2-1 in the Turkish Super League. Erdogan said the timing of the attack aimed to maximize the loss of life.

Soylu said the first explosion was caused by a passing vehicle that detonated in an area where police special forces were located at the stadium exit. A riot police bus appears to have been the target.

Moment later, a person who had been stopped in nearby Macka Park committed suicide by triggering explosives, according to the minister.

#Istanbul attack: Scenes from the aftermath of the twin blasts that killed at least 15 people and wounded dozens https://t.co/twpCDdU839 pic.twitter.com/X0txUpGLp4 — CNA (@ChannelNewsAsia) December 11, 2016

The civilian death toll was lower because fans had already left the newly built Vodafone Arena Stadium after the soccer match when the blasts occurred. Witnesses also heard gunfire after the explosions.

Soylu said 136 people remained hospitalized Sunday after the attack, including 14 under intensive care.

Forensic experts in white uniforms worked overnight, scouring the vicinity of the stadium and the vast park where the suicide bombing took place. Glass from the blown-out windows of nearby buildings littered the pavement.

Authorities have determined that about 300-400 kilograms of explosives were used in the attack, Kurtulmus told CNN Turk.

Vehicle and pedestrian traffic tentatively resumed Sunday in the blast area, which municipal workers rushed to clean up.

1 / 7Turkish football shout slogans on December 12, 2016 near the vodafone arena in Istanbul, during a demonstration following the attacks on December 10. T(AFP / Getty Images) 2 / 7Turkish football shout slogans on December 12, 2016 near the vodafone arena in Istanbul, during a demonstration following the attacks on December 10. (AFP / Getty Images) 3 / 7Turkish football supporters hold a giant Turkish national flag and shout slogans on December 12, 2016 near the vodafone arena in Istanbul, during a demonstration following the attacks on December 10. (AFP / Getty Images) 4 / 7Family members, army commanders and security officials attend funeral prayers for police officer Mehmet Zengin, 20, who was killed with dozens others late Saturday outside the Besiktas football club stadium Vodafone Arena in Istanbul, in Ankara, Turkey, Monday, Dec. 12, 2016. (AP Photo/Burhan Ozbilici)(AP) 5 / 7Istanbul-based foreign diplomates hold flowers as they walk to the attack site to remember dozens of people killed late Saturday outside the Besiktas football club stadium Vodafone Arena, in Istanbul, Monday, Dec. 12, 2016. (AP Photo/Emrah Gurel)(AP) 6 / 7Istanbul-based foreign diplomates hold flowers to remember dozens of people killed late Saturday outside the Besiktas football club stadium Vodafone Arena, in Istanbul, Monday, Dec. 12, 2016.(AP Photo/Emrah Gurel)(AP) 7 / 7Police officers carry the coffin after funeral prayers for police officer Huseyin Dalkilic, who was killed with dozens others late Saturday outside the Besiktas football club stadium Vodafone Arena in Istanbul, in Izmir, Turkey, Monday, Dec. 12, 2016. (AP Photo/Emre Tazegul)(AP)

Mourning, protests

At noon, to the mournful sound of trumpets, funeral services were held at Istanbul's police headquarters for some of the slain police officers with the country's top brass in attendance. Their comrades solemnly carried the coffins, which were draped in the Turkish flag, as mourners wept.

This year Istanbul has witnessed a spate of attacks attributed by authorities to the Islamic State group or claimed by Kurdish militants. A state of emergency is in force following a failed July 15 coup attempt.

Saturday's incident marked one of the bloodiest to hit the bustling city at the crossroads of Europe and Asia. A triple suicide-and-gun attack on the city's Ataturk Airport in June killed 44 people and wounded scores of others. Kurdish-linked militants have claimed other deadly attacks in Ankara, Istanbul and areas of the southeast.

The steady stream of violence has delivered a bitter blow to Turkey's tourism sector, a mainstay of the country's economy. Soylu acknowledged the country was struggling against "many elements" trying to compromise its fight against terrorism.

Turkey is a partner in the U.S.-led coalition against the Islamic State and its armed forces are active in neighboring Syria and Iraq. It is also facing a renewed conflict with an outlawed Kurdish movement in the southeast.

Condemnations of the attack came from a range of Turkish politicians, sports leaders and clubs and U.S. and EU officials.

Turkey's pro-Kurdish People Democratic Party, or HDP, issued a statement "strongly condemning" the attacks and saying it "felt great sadness and shared in the sorrow."

Turkish authorities, particularly the president, have routinely accused the party of being linked to the PKK and backing terrorism. The party, which had both of its leaders detained in terror probes and multiple elected officials arrested or removed from public service in the southeast, denies the charge.

The chair of the main opposition Republican People's Party also condemned the attack.

Ned Price, a spokesman for the White House National Security Council, said Washington condemned the attack in "the strongest terms."

"We stand together with Turkey, our NATO Ally, against all terrorists," Price said.

The Besiktas sports club "strongly condemned" the attack and said a store employee and a security official were among the fatalities. Bursaspor issued a statement wishing "a speedy recovery to our wounded citizens."

Aleksander Ceferin, president of European soccer's governing body UEFA, and European Union Enlargement Commissioner Johannes Hahn also condemned the attack.

"Violence has no place in a democratic society," Hahn wrote on Twitter.

The U.S. Consulate General in Istanbul urged its citizens to avoid the area in Istanbul.

Turkey's radio and television board issued a temporary coverage ban citing national security concerns. It said "to avoid broadcasts that can result in public fear, panic or chaos, or that will serve the aims of terrorist organizations."

By Mirjam Schmitt and Constanze Letsch / Deutsche Presse-Agentur GmbH (Hamburg, Germany) Additional details by Dominique Soguel / Associated Press