The US deployment of Patriot missiles in Turkey began on Saturday to help the country defend itself against any threat from neighbouring Syria which is in the throes of a deadly 21-month civil war.

"The deployment started early this morning into Incirlik" Air Base in southeastern Turkey, Peter Woodmansee, missile defence chief of the US European Command, told AFP.

"Several aircraft landed very early this morning with the advance party personnel from 3-2 Air Defense Artillery (ADA) -- the Patriot unit -- arriving as well."

The deployment comes as violence rages across Turkey's southern border, with the United Nations estimating that at least 60,000 people have been killed in Syria since the revolt against President Bashar al-Assad erupted in March 2011.

US military personnel and equipment began arriving Friday at Incirlik to support NATO Patriot batteries being deployed at Ankara's request.

The United States will transport some 400 troops to Turkey in the coming days to operate two Patriot batteries, the Stuttgart, Germany-based US European Command said in a statement on Friday.

Additional equipment will arrive by sea later in January.

The Americans will be based at Gaziantep, 50 kilometres (31 miles) north of the border.

"The 23 US team members at Gaziantep are determining specific site preparations the US and the government of Turkey must complete before we put the Patriot firing batteries at Gaziantep," Woodmansee said.

"Specifically, living area requirements, logistics, communications, safety and operational aspects of protecting the population in and around Gaziantep in support of the NATO defensive mission."

Germany, The Netherlands and the United States agreed to supply the ground-to-air missile batteries, which Turkey requested after repeated cross-border shelling from Syria, including an October attack that killed five civilians.

The Germans will be based at Kahramanmaras, some 100 kilometres north of the border and the Dutch at Adana, about 100 kilometres west of the border.

The Patriot systems are expected to become operational later this month.

Syria's allies Iran and Russia oppose the Patriot deployment, fearing that it could spark regional conflict also drawing in NATO.

"This mission is purely defensive in nature," said Woodmansee.

Iranian Foreign Minister Ali Akbar Salehi is visiting Cairo on January 9 for talks on Syria with Egyptian officials and possibly with UN-Arab League envoy Lakhdar Brahimi, according to Iranian media reports.

The Patriots would be deployed "to augment Turkey's air defence to de-escalate the situation along the Alliance's border," Woodmansee said, adding that positioning them 50 kilometres away would not compromise their effectiveness.

"Not at all -- the NATO mission is to protect the population. This is why the US, Dutch and German units will deploy near population centres," he said.

NATO-member Turkey, a one-time Damascus ally, has become one of its most vocal opponents over the more than 21-month civil war in Syria.

On Saturday at least 57 people, including 25 civilians, were killed there, said the Syrian Observatory for Human Rights, which reported violence in Damascus and areas around the airport in the northern province of Aleppo.

A shell hit Bab Tuma, a Christian area of Damascus, and a car bomb exploded in the capital's Rokn Eddin district, it said.

Assad's forces bombarded rebel positions in Aleppo province and clashes broke out in areas around Aleppo international airport, said the Observatory, which gathers its information from medics and activists on the ground.

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