The first Patriot missile batteries being sent by NATO countries to defend Turkey from possible attack from Syria are expected to be in place and ready for use this weekend, a senior NATO officer said on Wednesday.

The United States, Germany and the Netherlands are each sending two Patriot batteries and up to 400 soldiers to operate them after Ankara asked NATO for help to beef up its air defenses against possible missile attack from Syria.

Some Syrian shells have landed inside Turkish territory during the 22-month uprising against President Bashar al-Assad, prompting Turkish retaliation.

NATO says several Scud missiles fired by the Syrian army at rebels have landed near the Turkish border.

The six Patriot batteries are being stationed around three southeastern Turkish cities and NATO says they will protect 3.5 million Turks from missile attack.

The Dutch army will be the first to have some of its Patriots in place and that is expected to happen this weekend, said British Brigadier-General Gary Deakin, director of the Strategic Operations Centre at Supreme Headquarters Allied Powers Europe, which oversees NATO military operations.

All the Patriot batteries are expected to be in place and operational by the end of January, he told a news briefing at NATO headquarters.

"We expect to have an initial operating capability this weekend, that is what we are aiming at ... The first units will arrive on station, they will plug in to the NATO command and control network and they will be then ready to defend the population," Deakin said.

Initial plans are for the Patriot batteries to stay in Turkey for at least a year, he said.