ISTANBUL, Feb. 22 (Xinhua) -- Turkey's strong reaction against the entry of pro-Damascus forces into Afrin, where Turkish troops are fighting Kurdish militia, has to do with concerns that the move could undermine Ankara's plans at home and in Syria, according to analysts.

Damascus' involvement in Afrin would bust Ankara's hope of creating a Sunni zone in northern Syria, Hasan Koni, a professor of public international law at Istanbul Kultur University, told Xinhua.

Turkey is widely believed to be seeking to forge a Sunni-dominated area along its border in northwestern Syria by supporting the Free Syrian Army (FSA) and some moderate rebel groups in Idlib province.

As the advance of the Turkish army gained momentum on Tuesday in the Kurdish militia-held Afrin district, reports came that some pro-government forces arrived in Afrin to help the Kurdish militants counter the Turkish offensive.

Turkish President Recep Tayyip Erdogan said later that day that the convoy of the pro-regime fighters had to turn back without making it to Afrin under artillery shelling by Turkish troops.

Underlining Turkey's determination to not allow any such move, Erdogan warned that those attempting to aid the Kurdish militia, known as the People's Protection Units (YPG) which is treated by Ankara as a terror group, would pay a heavy price.

Some pro-government militia as well as Syrian army forces have managed to enter Afrin despite Turkish shelling, according to some press reports.

Citing Syria's state-run Sana news agency, Russia's Sputnik reported on Wednesday that new units of Syria's popular militia had made it to Afrin to fight against the Turkish army.

The pro-government forces are Shiite militia close to Iran, according to some reports.

The Syrian government, with which Ankara refuses to communicate politically, sees the Turkish army's presence on Syrian soil as an invasion and an assault on its sovereignty.

"Ankara reacts because whatever strategy and plans were made for Afrin and later for Manbij could now be thwarted," Faruk Logoglu, a former senior diplomat, told Xinhua.

Ankara said its troops would also move eastward, following the Afrin operation, to kick the YPG out of the town of Manbij, where U.S. troops are based.

On Jan. 20, Turkish troops, backed by FSA militants, launched Operation Olive Branch to drive the YPG out of Afrin, but they have advanced slower than expected so far, heightening concerns about more risks in the quagmire of the Syrian theatre involving world and regional powers as well as shifting alliances.

Ankara's attitude may also have to do with the critically important presidential and parliamentary elections scheduled for November 2019, Koni feels.

Noting the ruling Justice and Development Party (AKP) is exploiting the Afrin operation to win public support, he said any involvement of the Syrian forces would risk a success story in Afrin.

The AKP has been much criticized by the opposition for politically using the Afrin operation, as it is widely argued that success in Afrin would make snap elections more probable.

Reports have long circulated about Kurdish militia negotiating with Damascus to hand over the control of the Afrin canton to the Syrian army.

Turkish Foreign Minister Mevlut Cavusoglu warned on Monday that the operation would continue in case Syrian forces, including the Syrian army, would arrive in Afrin to protect the YPG rather than fight it.

The Syrian government's control of Afrin is probably viewed by Ankara as a preemption of Turkish influence in the region, observed Logoglu.

For Koni, the Turkish government may have plans about uniting Afrin with Idlib and then leaving them to FSA's control.

Under a deal with Russia and Iran aimed at ending clashes in Syria, Turkish troops have set up six observation posts in Idlib province, the only major stronghold for jihadist rebels now in the war-torn country.

There have been reports in the past suggesting Ankara's good ties with some jihadist groups in Idlib, where Tahrir al-Sham, formerly known as al-Nusra Front, is the leading force.

Turkey's Hurriyet daily said at the end of January that militants of Tahrir al-Sham escorted a Turkish military convoy heading toward the town of al-Ais in Idlib.

The AKP has been often criticized at home for supporting terror groups in Syria and for acting as patron to jihadist groups in Idlib, some of which represent moderate rebels for Ankara.

In December, Syrian Foreign Minister Walid al-Moualem accused Ankara of having designs on Syrian territory, while Ankara has repeated its claim about respecting the neighbor's territorial integrity.

Turkey has already controlled a swathe of Syrian territory since it completed in March last year a military operation in northern Syria aimed at driving the Islamic State away from the Turkish border and preventing the three Kurdish cantons from uniting along the border.

The land under Turkish control lies between the Afrin canton and the eastern side of the Euphrates River.

Top Turkish officials have often said that the areas cleared by the Turkish army from terror groups in Syria would be handed over to locals rather than the Syrian government.

President Erdogan said recently some of the around 3.5 million Syrian refugees being sheltered in Turkey would be settled in Afrin after the area is cleared of the YPG militants.

Yet another reason for Ankara's outcry against the presence of pro-Damascus forces is that both Syrian President Bashar al-Assad and the YPG are regarded as foes by Ankara, said Logoglu.

Such a perception would make any agreement between them as a collusion against Turkey, he noted.

In case the YPG hands over Afrin to Damascus, the legitimacy of the Turkish operation would be highly questionable. Turkey would then appear as a country that has declared war against Syria rather than as one fighting terrorism, said Koni.

Logoglu maintained that a clash between the Turkish and Syrian armies is most unlikely because it is a scenario the Russians would make efforts to circumvent.

Arguing that Russia's presence in Syria depends on the survival of al-Assad, he said, "Russia therefore will not put al-Assad at risk, knowing he would suffer defeat in any confrontation with the Turks."

Russian Foreign Minister Sergei Lavrov has called for Ankara to settle its security concerns through direct dialogue with Damascus, while Ibrahim Kalin, Erdogan's spokesman, rejected on Wednesday the establishment of any "political dialogue" with the Syrian government.