Damascus has demanded Turkish troops leave the Syrian city of Afrin - after they seized the region's main town from Syrian Kurdish fighters at the weekend.

'The announcement of Turkish regime's president that his invading forces control Afrin is illegitimate,' the Foreign Ministry said in letters to the United Nations.

'Syria demands the invading forces withdraw immediately from the Syrian lands they have occupied.'

President Recep Tayyip Erdogan has vowed the Turkish army will drive Kurdish forces out of northern Syria on Monday following the capture of Afrin district

But Turkey has vowed to continue expanding its Syria offensive.

President Recep Tayyip Erdogan vowed on Monday to 'entirely eliminate' Kurdish forces on the Syrian side of the Turkish border.

He also raised the prospect of launching surprise attacks on Kurdish positions in Iraq, which is a strategic partner of the US.

Kurdish fighters formed the backbone of the US-backed Syrian Democratic Forces which were instrumental in defeating ISIS.

Turkish forces along with allied rebel groups (pictured) will 'entirely eliminate' Kurdish forces from along Turkey's border, Erdogan said

Erdogan said the Turkish campaign in Syria, conducted in tandem with Syrian forces, could now extend east, following the Turkish border to the town of Qamishli, the last Kurdish-held town before the Iraqi border.

'Now we will continue this process until we entirely eliminate this corridor, including in Manbij, Ayn al-Arab, Tel-Abyad, Ras al-Ayn and Qamishli,' Erdogan said.

Manbij, the next main YPG-held town east of Afrin, is a particular flashpoint as there is a US military presence there, raising the risk of confrontation between NATO allies.

Ayn al-Arab is the border town known as Kobane in Kurdish, of symbolic importance as it was the epicentre of a struggle with Islamic State jihadists that saw the US lauch its first airstrikes in Syria.

Turkish forces had watched from across the border as ISIS swept down on the city.

Turkey has been involved in conflict with Kurdish separatists for decades as they demand their own state, which would fall partially on Turkish territory.

Erdogan even raised the prospect of surprise attacks against Kurdish forces in Iraq, a key US strategic partner in the region (pictured, Turkish-backed rebels in Afrin)

Kurdish forces formed the backbone of the US-backed Syrian Democratic Forces which helped to defeat ISIS (pictured, smoke rises over Afrin)

Turkey sees the YPG as a Syrian offshoot of the outlawed Kurdistan Workers' Party (PKK), which has waged a bloody insurgency against the Turkish state since 1984.

Most of Afrin's 350,000 residents have fled since Turkey and allied Syrian rebels launched an air and ground offensive on January 20 to root out the YPG.

The capture of the city is seen a major step forwards for Turkey as it seeks to bolster its control along the border in northern Syria.

Erdogan described Afrin's capture after almost two months as a 'major stage' of the operation, codenamed Olive Branch. But he said more would come.

'We marked a comma. God willing a full stop will come next.'

But he insisted that Turkey 'has no intention of being occupiers' in Syria and only wanted to remove the threat posed by the 'terrorists.'

Syrian President Bashar Assad was seen in a video released by the Facebook page of the Syrian Presidency

Footage shows him driving through the newly captured areas of eastern Ghouta, near Damascus

Observer groups said Turkish-backed rebels began looting the city after capturing it, with masked figures pictured with tractors full of goods

A Turkish-backed rebel fighter drags a car away with a tractor after capturing Afrin

He also evoked a possible operation against PKK camps in Iraq's Sinjar region, saying this could come any time.

Erdogan said he had told the Iraqi authorities in Baghdad to deal with PKK camps there, warning Sinjar risked becoming one of the group's strongholds, like the Qandil mountain area.

'If (Baghdad) cannot, we may turn up in Sinjar suddenly one night and clean up the PKK there.'

Erdogan spoke as Turkish-backed Syrian rebels were accused of looting in Afrin following the capture of the city.

Monitoring groups said shops, military and government facilities had been raided, while pictures showed masked figures making off with tractor trailers full off goods.