The Kurdish militia-led Syrian Democratic Forces (SDF) on Wednesday declared a three-day state alert in preparation for the Turkish incursion.

"As threats and mobilization of the Turkish Army and its mercenaries escalate ... we call on our people ... to go to the area bordering Turkey to carry out their moral duty and show resistance at these sensitive historical moments," an SDF statement said.

Turkish Foreign Minister Mevlut Cavusoglu said Turkey will inform all relevant countries and the United Nations about its operations into northeast Syria.

Speaking in a news conference in Algeria, Cavusoglu said the operation will be carried out in accordance with international law and that Turkey will only target militants in the region.

Read more:  Why Turkey wants a military assault on Syrian Kurds

According to a local broadcast citing Turkish Defense Minister Hulusi Akar on Wednesday, the Turkish army's preparations continue.

An aide to Turkish President Tayyip Erdogan said the Turkish army and its Syrian rebel allies would cross the Syrian border "shortly." The Turkish government has said the Syrian Kurds are linked to the outlawed Kurdistan Workers Party (PKK), which Ankara, the European Union and the United States regard as a terrorist organization.

According to Turkish state media, more than 100 vehicles carrying troops, weapons and construction equipment were sent to Sanliurfa's Akcakale district, 6 kilometers (3.7 miles) from the strategic border town of Tal Abyad. The Syrian Observatory for Human Rights, a British-based monitoring group, reported Wednesday that people of Tal Abyad were fleeing as many expect it could be under attack first. 

US troops on Monday started pulling back from areas in northeastern Syria, paving the way for a Turkish incursion. The SDF had been a central partner in the US effort to defeat the "Islamic State" in Syria. US President Donald Trump abruptly announced on Sunday that American troops would step aside for Turkey's push. He then tweeted, "if Turkey does anything that I, in my great and unmatched wisdom, consider to be off limits, I will totally destroy and obliterate economy of Turkey," adding that Europe must "watch over."

Read more:  Trump's Syria withdrawal: Who stands to gain?

Iran: Syrian army 'the only solution'

In reaction to the incursion preparations, Iran called on Turkey to avoid military conflict in northern Syria. 

Iranian President Hassan Rouhani, a close ally of Syrian President Bashar-Al-Assad, told state media that the "presence of the Syrian army" is the "only solution to ensure safety and security in southern Turkey and northern Syria."

Iran has warned Turkey several times to respect Syria's territories and urged all foreign military forces "with an illegal presence," including the US, to leave Syria. 

"We are calling on our friendly and brotherly neighbor Turkey to act with more patience and restraint, and to revise its decision."

Read more: Turkey clamps down on Syrian refugees

'Safe zone'

Erdogan's administration has announced it plans to establish a "safe zone" in northeastern Syria to resettle around 2 million Syrian refugees there, alarming Western allies. 

Turkey's foreign minister also said on Wednesday that Erdogan had informed Trump of the planned offensive over the weekend after Washington delayed Turkey's efforts to create the safe zone. 

Ankara has said it intends to secure a stretch of territory along its southern border with Syria that runs more than 480 kilometers (300 miles) long toward the Iraqi border and is 30 kilometers deep.

mvb/sms (AP, AFP, dpa, Reuters)

Every evening, DW sends out a selection of the day's news and features. Sign up here.