DAMASCUS - The Turkish forces on Tuesday evening shelled a position of the Kurdish-led Syrian Democratic Forces (SDF) in northern Syria without causing human losses, a well-informed Kurdish source told Xinhua.

The source, who is close to the SDF, told Xinhua on condition of anonymity, that the artillery shelling targeted an SDF position in the Ras al-Ayn area, known in Kurdish as Sari Kani, in the countryside of the northeastern province of Hasakah.

The Syrian Observatory for Human Rights war monitor also reported the Turkish shelling on Ras al-Ayn, saying it comes in tandem with the arrival of more Turkey-backed Syrian rebels to the Turkish territories to take part in the planned Turkish military campaign against the Kurdish forces in northern and northeastern Syria.

The shelling comes after US President Donald Trump warned the previous day Ankara against the repercussions going "off-limits" in the planned offensive against the US-backed SDF.

"If Turkey does anything that I, in my great and unmatched wisdom, consider to be off-limits, I will totally destroy and obliterate the Economy of Turkey," Trump said in a tweet after he ordered the withdrawal of US forces from two observation points near the Syrian-Turkish border.

The withdrawal of the US forces was criticized by the Kurdish militia, as the United States has been their main support in northern Syria.

In a tweet on Tuesday, Trump said the United States wasn't abandoning the Kurdish fighters.

Syria's national TV said Monday evening that Turkish forces targeted positions of the SDF in northern and northeastern Syria.

The Observatory, however, denied the official Syrian report about the beginning of a Turkish campaign against the Kurdish fighters on Monday.

Also Monday, Turkish President Recep Tayyip Erdogan said that Ankara was ready to launch military operations against the People's Protection Unit (YPG) and its allies of the SDF in the east of the Euphrates in northern Syria "at any moment."

Turkey sees the YPG and its allied SDF as separatists and terrorists, citing their links with the Kurdistan Workers' Party (PKK), which is listed as a terrorist organization by Turkey, the United States, and the European Union.

The Kurdish militia forces have been controlling areas in northern Syria since the early years of the crisis in Syria, in order to force Damascus to recognize a federal rule or autonomy for the Kurds in northern Syria.

However, Syrian government officials repeatedly said that Kurdish federalization in Syria or self-rule is out of the question.

As a response to the Turkish threats of launching a military campaign in Syria, Syria's Deputy Foreign Minister Faisal Mekdad said Tuesday that the Syrian government will defend all Syrian areas and will not accept any form of occupation by foreign forces.