ISTANBUL — Moscow accused Ankara of endangering Russian lives on Thursday after Turkey forced a Syrian passenger plane to land and seized what it suspected was military equipment being ferried from Russia to Syrian President Bashar al-Assad.
Damascus said intercepting the Syrian Air plane was an act of piracy, further heightening tensions between the neighbors after Turkey's chief of staff warned Ankara would use greater force if shells from Syria continued to hit Turkish territory.
The grounding of the plane was another sign of Ankara's growing assertiveness over the crisis in Syria following almost a week of retaliation by its armed forces to gunfire and shelling spilling across the border.
"Turkey has crossed a new threshold," said former Turkish diplomat Sinan Ulgen, chairman of the Centre for Economic and Foreign Policy Studies think tank. "With the action they took last week the government is in the slightly more comfortable position of having shown it has the strength to retaliate."
Military jets escorted the Damascus-bound Airbus A-320, which was carrying around 30 passengers from Moscow, into Ankara airport late on Wednesday after Turkey received intelligence that it was carrying "non-civilian cargo."
Russia, which has stood behind Assad's government during an 18-month-old uprising that has killed some 30,000 people, angrily demanded an explanation.
"The lives and safety of the passengers were placed under threat," the Russian Foreign Ministry said in a statement, adding that 17 of its nationals onboard were refused access to Russian diplomatic staff.
Russian President Vladimir Putin had been expected to visit Turkey at the start of next week but Turkish officials said hours before the plane was grounded that Russia had requested the visit be postponed, citing his heavy work schedule.
He was now expected on Dec. 3, an official in the Turkish prime minister's office said. Russian officials could not immediately be reached for comment.
None of the plane's passengers were arrested and officials did not say what was confiscated. Turkish media said the cargo included non-lethal military supplies such as radio equipment.
Syrian Air chief Ghaida Abdulatif told reporters in Damascus the plane was carrying civilian electrical equipment that was allowed to be transported and had been officially registered.
Lebanon's al-Manar Television quoted Syrian Transport Minister Mahmoud Said as saying the move amounted to "air piracy which contradicts civil aviation treaties."
"BRUTAL MASSACRES"
Turkey said it would stop more civilian aircraft using its airspace if necessary and instructed Turkish passenger planes to avoid Syrian airspace, saying it was no longer safe.
"We are determined to control weapons transfers to a regime that carries out such brutal massacres against civilians. It is unacceptable that such a transfer is made using our airspace," Foreign Minister Ahmet Davutoglu said.
"We received information this plane was carrying cargo of a nature that could not possibly be in compliance with the rules of civil aviation," he said.
Turkey has become one of Assad's harshest critics, providing sanctuary for rebel officers and fighters and pushing for a foreign-protected safe zone inside Syria.
Washington sees Turkey as the key player in supporting Syria's opposition and planning for the post-Assad era, but Ankara has found itself increasingly isolated and frustrated by a lack of international consensus on how to end the chaos.
Turkey has boosted its troop presence along the 900-km (560-mile) border and returned fire over the past week in response to shelling from northern Syria, where Assad's forces have been battling rebels who control swathes of territory.
Turkish Chief of Staff General Necdet Ozel said on Wednesday his troops would respond "with greater force" if the shelling continued and parliament last week authorised the deployment of troops outside Turkish territory.
"If the killing of civilians is repeated, Turkey will use the authority given to it by parliament to cross the border and at the very least establish a buffer zone, which it has asked the international community to set up," said Kamer Kasim, vice-president of the Ankara-based International Strategic Research Organization.
RISKS OF DEEPER INVOLVEMENT
The conflict threatens to spill over Syria's borders and ignite a wider Middle Eastern war pitting Sunni Muslim states against Syria's rulers and their allies including Shi'ite Iran.
But Turkey has repeatedly made clear that beyond like-for-like retaliation it has no appetite for unilateral intervention in Syria. Such a move would be fraught with risks.
Russia, from where the Syrian plane took off, has blocked tougher U.N. resolutions against Damascus and the grounding of the plane further tested relations with Ankara, which has pushed for a safe zone inside Syria patrolled by foreign aircraft.
The row with Moscow highlights the dangers for Turkey of deeper involvement in Syria. Turkey relies on Russia both for its domestic energy needs and for the resources to realize its greater ambitions as a hub for energy supplies to Europe.
Historically, many Turks and Kurds inside Turkey saw the Soviet Union as an important source of funding for the Kurdish Workers Party (PKK), a Kurdish militant group deemed a terrorist organisation by Turkey, the United States and European Union.
Many of them still see Russia as harboring sympathy towards the group, which has stepped up its campaign of violence in southeastern Turkey in recent months, and Turkish officials believe Syria and Iran have also been backing the PKK.
"We get 80 percent of our natural gas from Iran and Russia. Already the PKK card is being used by Iran against Turkey . . . so the risks for Turkey of being involved in even a limited operation are huge," Ulgen said.
Even the establishment of foreign-protected safe zones would be hazardous, with the exit strategy for foreign forces dependent on the Syrian opposition's ability to topple Assad.
"We would be hostage to their fortunes and as long as they failed to deliver, Turkey would be faced with the risks of a deteriorating international context," Ulgen said.
The rebels are outgunned by the government but can still strike at will, while Assad has assumed personal command of his forces, convinced he can prevail militarily.
Rebels attacked a Syrian army base near the main northern highway on Thursday to try to consolidate their control over the supply line to Aleppo, days after capturing a strategic town in the area, opposition activists said.
They used at least one tank seized from the army, as well as rocket-propelled grenades and mortar bombs, to hit the Wadi al-Deif base, three kilometers (2 miles) east of the town of Maarat al-Nuaman, which they captured this week, they said.
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