Turkey has been shelling targets in northern Syria for the past week in a bid to stem the advances of a Kurdish-led coalition that has seized territory in the area.

Ankara blames Syrian Kurdish fighters for this week's suicide car bomb attack in the Turkish capital that killed 28 people and fears the creation of a Kurdish stronghold along its southern border.

"The situation we are currently facing is one of legitimate defence. No-one can deny or limit Turkey's legitimate right to defence in the face of terrorist attacks" Erdogan said in a speech in Istanbul late on Saturday according to the Dogan news agency.

Erdogan's remarks come after the United States France and Russia all urged Turkey to scale back or halt its military action in Syria.

US President Barack Obama in a phone call with Erdogan on Friday urged the Ankara government and the Kurdish People's Protection Units (YPG) militia to "show reciprocal restraint" in northern Syria.

French President Francois Hollande warned that Ankara's escalating involvement in the conflict was creating a risk of war between Turkey and Russia which back different sides in Syria's increasingly complex civil war.

Ankara says the YPG is a branch of the outlawed Kurdistan Workers' Party (PKK) which which has waged a three-decade insurgency against the Turkish state and is recognised as a terror group by the United States and EU.

Earlier this week Erdogan vowed not to allow the creation oif a Kurdish stronghold in northern Syria saying there was no question of stopping the artillery barrage.

"To fight the threats which it faces Turkey has the right to launch any kind of operation in Syria and wherever else the terrorist organisations are located" Erdogan said.

The Turkish leader also again criticised the United States without mentioning it by name for its "lack of sincerity" about Turkey's worries over Syrian Kurdish fighters.

Washington supports the Syrian Kurdish Democratic Union Party (PYD) and its YPG militia as the best fighting force on the ground against Islamic State (IS) jihadists. Turkey considers both to be terror groups linked to the PKK.

Some 21 suspects held over the Ankara attack were due to appear in court on Sunday the pro-government Anatolia news agency reported.