Turkish President Recep Tayyip Erdogan vowed to unleash an "iron fist" against terrorism on Wednesday, dismissing calls for democratic values as police detained dozens, including lawyers and academics, in what authorities called anti-terror raids.

The fighting tone and threats come as Turkey blames Kurdish militants for a car bombing in Ankara on Sunday which killed 37 people. No group has claimed responsibility for the attack, which took place as fighting in the mostly Kurdish south-eastern Turkey intensified.

Erdogan slammed those who criticize Turkey over values like "democracy, freedom and rule of law," in a speech in Ankara to local district leaders.

"For us, these phrases have absolutely no value any longer," he said in the televised address. "Those who stand on our side in the fight against terrorism are our friend. Those on the opposite side, are our enemy."

The speech was punctuated with standing ovations and regular applause.

Earlier this week, Erdogan also pledged to broaden the definition of "terrorist" in Turkish law to include academics, journalists and civil society groups, who are deemed to be "accomplices."

The Wednesday remarks come ahead of a Turkey-European Union summit this week, with Brussels looking to Ankara to help stem the flow of irregular migration to the bloc. Rights activists have been critical of the EU, demanding a tougher stand on Turkey's human rights issues.

The legal pro-Kurdish Peoples' Democratic Party (HDP), which has 59 seats in parliament, was also a focus of Erdogan's anger, with the president calling the group illegitimate and out of bounds for cooperation.

There is concern about ongoing legal proceedings which could end in outlawing the HDP or its members, in a move that could further polarize the country and alienate the Kurdish minority, which comprises at least 15 per cent of the population.

Turkish police detained 47 people Wednesday, including lawyers, following a wave of raids which saw 79 people taking into custody on Monday - all, according to the state-run Anadolu news agency, targeting the Kurdistan Workers' Party (PKK), which is banned.

Three academics were meanwhile charged and are being held in custody for alleged support for terrorism, their colleagues said on social media.

The academics are among a group of some 1,000 lecturers and educators who signed a declaration calling for peace in Turkey and denounced the state security forces' crackdown in mostly Kurdish parts of the country, according to Anadolu and a Human Rights Watch statement.

A British academic who works at an Istanbul university was also detained for supporting those under arrest, colleagues said on social media, adding that he faces deportation.

Salih Muslim, the head of the largest Syrian Kurdish faction, the Democratic Union Party (PYD), rejected accusations from Turkey that his group had any involvement in the Ankara attacks and condemned the car bombing. He was attending a conference in northern Iraq.

Erdogan was critical of Western nations for supporting the PYD in Syria, whose armed wing is the main ally of the United States in pushing back Islamic State in the country.

Turkey last month accused the group of involvement in an attack in Ankara, though this turned out to be discredited when another organization claimed the bombing.

Press freedom groups have been on edge this week after Erdogan vowed to expand the definition of terrorist.

"Just because they have titles such as a legislator, an academic, an author, a journalist or head of an civil society organization, does not change the fact that they are actually terrorists," Erdogan said on Monday in Ankara, in the opening salvo of his latest denunciations.

There are numerous journalists in the country already in jail or facing trial, and there has been a crackdown on freedom of expression using a law which makes it illegal to insult the president.

A two-year ceasefire between Turkey and the PKK collapsed in July amid mutual recriminations and a collapse of peace talks. The Kurdish militants, who have been fighting the state for three decades, are demanding greater autonomy and right for the minority group.

The state stepped up military operations against the PKK and other groups in December.

Since then, hundreds have died, including civilians. There has been wide-scale destruction in some Kurdish districts and more than 350,000 people were displaced.

The conflict continues to spread to more districts in cities in the south-east.

Analysts say the last car bombing in Ankara, if indeed carried out by Kurdish nationalists, as well as similar attack last month which killed 30 and claimed by a splinter group, are a sign that the violence cannot be contained in one part of the country.

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