Kurdish militant group says it carried out Istanbul bombings that killed 38

People stand hand in hand outside the Besiktas football club stadium Vodafone Arena in Istanbul following the two Turkish blasts. Photo / AP

A shadowy Kurdish militant group has claimed responsibility for a pair of bombings that killed dozens of people outside a stadium in central Istanbul, 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 today that two of its members carried out the attacks.

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

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

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

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 Sunday comes as part of a string of terrorist attacks by both Kurdish and Isis (Islamic State) militants across Turkey in recent years.

The violence has threatened to destabilise 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 declared a national day of mourning, and officials vowed to pursue Kurdish militants.

Turkish Prime Minister Binali Yildirim said that the attack was an opportunity for Turkish security forces to pursue the PKK, which has itself been locked in a conflict with the Turkish state for years, Reuters 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 per cent of Turkey's 75 million people. Analysts say that the TAK militants split with the PKK over negotiations with the Government, but that the two groups maintain strategic ties.

Sunday's blasts, which could be heard across Istanbul and sent up a plume of smoke, detonated outside the Vodafone Arena in the Beskitas neighbourhood, less than a kilometre from the bustling Taksim Square and on the edge of the Bosporus.

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 football match earlier in the day, 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 rise," Mehmet Ata Ekin, a 54-year-old employee of a cafe close to the arena, said of the first blast.

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

Today, outside the nearby Dolmabache Mosque, shards of glass from shattered windows littered the ground. Worshippers 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.