ISKENDERUN, Turkey: The first of six NATO Patriot missile batteries intended to protect Turkey from a potential Syrian attack arrived by ship from Germany on Monday, drawing a small but noisy protest from nationalist and leftist demonstrators.

Dozens of camouflaged German military vehicles carrying the batteries disembarked at the Mediterranean port of Iskenderun. About 150 Turkish Communist Party supporters fired pink smoke grenades and burned an American flag at a port entrance.

Germany, the Netherlands and the United States are each sending two Patriot missile batteries and up to 400 troops to Turkey after Ankara asked for NATO's help to bolster security along its 900-km (560-mile) border with Syria.

Damascus has called the move "provocative", in part because Turkey's missile request could be seen as a first step toward implementing a no-fly zone over Syrian airspace.

The frontier has become a flashpoint in the 22-month insurgency against President Bashar al-Assad, with Syrian government shells frequently landing inside Turkish territory, drawing a response in kind from Ankara's military.

"This mission is purely defensive," said Polish Army Lieutenant Colonel Dariusz Kacperczyk, NATO spokesman for the Patriot deployment. "It is to deter any possible threat coming from missiles to the Turkish population and territory."

The batteries will be fully operational by the beginning of February and will protect more than 3.5 million people living in the region, he said.

Turkey has been one of Assad's fiercest critics, leading calls for international intervention and providing shelter for more than 150,000 Syrian refugees. Despite wariness over a possibly more complex Turkish involvement in the conflict, there has only been small-scale opposition to the NATO deployment.

"Yankee go home!", "Murderer America, get out of the Middle East!", chanted a crowd of nationalists, some waving Turkish flags, at a later protest in the centre of Iskenderun.

"Iskenderun port will become NATO's grave", said a placard held by one in the hundreds-strong crowd. Riot police, backed by armoured water cannon vehicles, looked on from a distance.

Iran and Russia, which have supported Syria throughout the uprising, have criticised NATO's decision, saying the Patriot deployment would intensify a conflict that most foreign governments have been reluctant to get sucked into.

Turkey and NATO have strongly denied the Patriot missiles are a precursor to a no-fly zone that Syrian rebels have been requesting to help them hold territory against a government with overwhelming firepower from the air.

Tensions have increased in recent weeks after NATO said it had detected launches of short-range ballistic missiles inside Syria, several of which have landed close to the Turkish border. Turkey has scrambled war planes along the frontier, fanning fears the war could spread and further destablise the region.

The German Patriot batteries, whose deployment was approved by NATO in early December at Turkey's request, will travel by road convoy from Iskenderun to be deployed around the city of Kahramanmaras, some 100 km (62 miles) from the Syrian border.

The Dutch missiles, which are expected to arrive by ship in Iskenderun on Tuesday, will be stationed further to the west outside the city of Adana, about 120 km from Syria.

The U.S. missile batteries are expected to arrive later this month and will be deployed further to the east in Gaziantep, which is about 60 km from the frontier.

Advance troops as well as equipment from all three NATO countries had already begun arriving by air in preparation but Monday's delivery marks the first of the actual missile batteries to arrive on Turkish soil.