Relatives mourn over the coffin of a Turkish police officer killed during a pair of bombings Saturday in Istanbul. The attack left at least 38 people dead. (Ozan Kose/AFP/Getty Images)

A shadowy Kurdish militant group has claimed responsibility for a pair of bombings that killed dozens of people outside a stadium in central Istanbul on Saturday night, escalating an already bloody conflict between Kurdish separatists and the Turkish state.

The little-known Kurdistan Freedom Falcons (TAK) — which seeks autonomy for Turkey’s ethnic Kurds and opposes negotiations with the government — announced Sunday that two of its members carried out the attack.

The twin explosions, from a car bomb and separate suicide attack, killed 38 people, including 30 riot police; 155 other people were wounded.

“The Turkish people are not the direct target of TAK,” said the statement, which was posted online.

The group, an offshoot of the larger Kurdistan Workers’ Party (PKK), urged Turkish citizens to abandon support for the government.

People pray during an anti-violence demonstration outside the Vodafone Arena in Istanbul. (Yasin Akgul/Agence France-Presse via Getty Images)

A “comfortable life” is not possible in Turkey while the conflict continues, TAK said, adding: “The people of Turkey must now say no to this fascism.”

The carnage on Saturday comes as part of a string of terrorist attacks by Kurdish and Islamic State militants across Turkey in recent years.

The violence has threatened to destabilize a nation already roiled by domestic and regional crises. An attempted coup by a rogue faction of the military nearly toppled the government in July.

Authorities on Sunday declared a national day of mourning, and officials vowed to pursue Kurdish militants.

Turkish Prime Minister Binali Yildirim said the attack was an opportunity for Turkish security forces to pursue the PKK, which has been locked in a conflict with the Turkish state for years, the Reuters news agency reported.

Violence has surged since a peace agreement between the PKK and Turkish government fell apart in 2015, bringing terrorism to Turkish cities and devastation to largely Kurdish areas in the southeast.

Ethnic Kurds — who live across areas of Turkey, Iraq, Syria and Iran — make up about 20 percent of Turkey’s 75 million people. Analysts say that the TAK militants split with the PKK over negotiations with the government but that the groups maintain strategic ties.

Saturday’s blasts, which could be heard across Istanbul and which sent up a plume of smoke, detonated outside the Vodafone Arena in the Beskitas neighborhood, less than a mile from the bustling Taksim Square and on the edge of the Bosphorus.

Turkish Interior Minister Suleyman Soylu said the attack started with a car bomb that targeted a group of riot police posted at the stadium after a soccer match earlier Saturday evening, according to local media reports. The second explosion, which authorities attributed to a suicide bomber, happened less than a minute after the first, in a throng of police officers, Soylu said.

“We panicked. The ground shook, and smoke started to rise,” Mehmet Ata Ekin, a 54-year-old employee of a cafe close to the arena, said of the first blast Saturday night.

He ran to take shelter, “then all of a sudden, another explosion happened,” he said, followed by gunfire.

On Sunday, outside the nearby Dolmabahce Mosque, shards of glass from shattered windows littered the ground. Worshipers gathered for prayer, including a man draped in a Turkish flag. Others wore police jackets, and small crowds waving flags also made their way toward the blast sites.

The near-simultaneous bombs marked the deadliest attack in Istanbul in months, after suspected Islamic State operatives killed nearly 50 people at the city’s Ataturk Airport in June.

Saturday’s attack came hours after Turkey’s ruling Justice and Development Party submitted a bill to parliament that would grant sweeping powers to Turkish President Recep Tayyip Erdogan.

The bill proposes amending Turkey’s constitution to allow for a presidential rather than parliamentary system and would enable the increasingly authoritarian leader to run for additional terms.

Many pro-government newspapers splashed their front pages Sunday with praise for the proposed amendment.