Istanbul: Turkey declared a national day of mourning after twin blasts in Istanbul killed 38 people and wounded 155 others near a soccer stadium – the latest large-scale assault to traumatise a nation confronting an array of security threats.

The bombs on Saturday night targeted security forces, with at least 30 of the dead identified as police officers, Turkey's Interior Minister Suleyman Soylu told reporters on Sunday.

Prime Minister Binali Yildirim ordered flags to fly at half-mast on Sunday across the country and at Turkey's foreign missions.

Mr Soylu said 13 people had been arrested in connection with the "terrorist attack."

There was no immediate claim of responsibility for the attack, but Prime Minister Binali Yildirim said there was "almost no doubt" the attacks were the work of the militant Kurdistan Workers Party (PKK), which has carried out a three-decade insurgency, mainly in Turkey's largely Kurdish south east.  

Mr Soylu, speaking at a funeral at the Istanbul police headquarters for five of the officers killed, said Turkey would "sooner or later" reap vengeance.

"This blood will not be left on the ground, no matter what the price, what the cost," he said.

President Tayyip Erdogan was present but did not speak, although he greeted and hugged some of the family members.

Mr Soylu also warned those who would offer support to the attackers on social media or elsewhere, comments aimed at pro-Kurdish politicians the government accuses of having links to the PKK, which is designated as a terrorist organisation by the United States, Europe and Turkey.

"To those trying to defend the perpetrators from podiums, over the media or internet, and trying to make up excuses," he said. "There is no excuse for this ... Know this: the blade of the state stretches far and wide."

Deputy Prime Minister Numan Kurtulmus told the private news channel CNN Turk that "arrows point to the PKK".

The outlawed party has waged a decades-long insurgency. 

Mr Soylu said 136 people remained hospitalised after the attack, including 14 in intensive care.

The first and larger explosion took place about 7.30pm local time after the home team Besiktas beat visitors Bursaspor 2-1 in the Turkish Super League.

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

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

Turkish officials said a person who had been stopped in nearby Macka Park committed suicide by triggering explosives moments later.

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

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.

This year Istanbul has witnessed a spate of attacks attributed by authorities to the Islamic State group or claimed by Kurdish militants.

In recent months, thousands of Kurdish politicians have been detained including dozens of mayors and the leaders of the Peoples' Democratic Party (HDP), parliament's second-biggest opposition party, accused of links to the PKK.

The crackdown against Kurdish politicians has coincided with widespread purges of state institutions following a failed coup in July that the government blames on followers of a US-based Muslim cleric. 

Mr Soylu acknowledged the country was struggling against "many elements" trying to compromise its fight against terrorism.

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

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

It urged the government to end what it called the language and politics of "polarisation, hostility and conflict".

AAP, Reuters