Turkish artillery has shelled areas of Aleppo province in northern Syria held by Kurdish forces, a monitor said, as Turkey announces it could launch a ground assault against Islamic State with Saudi Arabia.

The military hit targets of the Syrian Kurdish Democratic Union Party (PYD) and the Syrian regime in two separate incidents in response to incoming fire, the state-run Anatolia news agency reported.

The army also responded to Syrian regime fire on a Turkish military guard post in Turkey's southern Hatay region, Anatolia added.

Key points: Turkey and Saudi Arabia may join forces and launch a ground operation against Islamic State jihadists in Syria

Turkey and Saudi Arabia may join forces and launch a ground operation against Islamic State jihadists in Syria Move comes as Syrian government forces advance into Raqqa province, Islamic State's de facto capital

Move comes as Syrian government forces advance into Raqqa province, Islamic State's de facto capital US Secretary of State John Kerry calls on Russia to stop bombing 'legitimate opposition groups'

US Secretary of State John Kerry calls on Russia to stop bombing 'legitimate opposition groups' Turkey shells Kurdish militia in northern Syria

Prime Minister Ahmet Davutoglu appeared to confirm the strikes against the PYD, without giving precise details.

"Under the framework of the rules of engagement, we responded to forces in Azaz and around that were posing a threat," he said.

Meanwhile, speaking after the Munich Security Conference, Foreign Minister Mevlut Cavusoglu said Turkey and Saudia Arabia would be willing to send troops to fight IS if required.

"If there is a strategy [against IS] then Turkey and Saudi Arabia could enter into a ground operation," he told the Yeni Safak and Haberturk newspapers.

"Some say Turkey is reluctant to take part in the fight against Daesh [IS] ... but it is Turkey that is making the most concrete proposals."

Mr Cavusogli added that Saudi Arabia, which has become an increasingly close ally of Turkey in recent months, would also be sending planes to the Turkish base of Incirlik to fight IS.

"They [Saudi officials] came, did a reconnaissance of the base. At the moment it is not clear how many planes will come," he said.

Incirlik is a key hub for US-led coalition operations against IS, with planes from Britain, France and the United States carrying out raids inside Syria from the base.

"They [Saudi Arabia] said 'If necessary we can also send troops'. Saudi Arabia is showing great determination in the fight against terror in Syria," Mr Cavusogli said.

Saudi Foreign Minister Adel al-Jubeir said in a German newspaper interview: "There is discussion on whether ground troops are needed against IS.

"If a decision is taken to send in special units against IS, Saudi Arabia is ready to take part."

Syrian government forces set sights on Raqqa

The comments came as Syrian government forces backed by Russian air strikes took rebel ground near Aleppo.

US Secretary of State John Kerry reiterated accusations that Russia was hitting "legitimate opposition groups" and civilians with its bombing campaign in Syria and said Moscow must change its targets to respect the ceasefire deal agreed on by major powers.

The agreement falls short of a formal ceasefire, since it was not signed by the warring parties — the Government and rebels seeking to topple President Bashar al-Assad.

Russian Foreign Minister Sergei Lavrov, asked at a security conference in Munich on Saturday to assess the chances of the cessation of hostilities deal succeeding, replied: "49 per cent."

Asked the same question, his German counterpart Frank-Walter Steinmeier put the odds at 51 per cent

Meanwhile the Syrian army looked poised to advance into the Islamic State-held province of Raqqa for the first time since 2014, apparently to pre-empt any move by Saudi Arabia to send ground forces into Syria to fight the jihadist insurgents.

A Syrian military source said the army captured positions at the provincial border between Hama and Raqqa in the last two days and intends to advance further.

"It is an indication of the direction of coming operations towards Raqqa. In general, the Raqqa front is open ... starting in the direction of the Tabqa area," the source said.

Tabqa is the location of an air base captured by Islamic State two years ago, and the source said the army had moved to within 35 kilometres of the base.

In another sign of escalation, Turkey's military shelled Kurdish militia targets near the northern Syrian town of Azaz on Saturday, a Turkish military source said.

A Kurdish official said the shelling targeted the Menagh air base in the northern Aleppo countryside, which he said had been captured by the Kurdish-allied Jaysh al-Thuwwar group.

Turkey strengthening ties with Assad's opponents

Saudi Arabia and Turkey both see the ousting of Mr Assad as essential for ending Syria's five-year civil war and are bitterly critical of Iran and Russia's support of the Syrian regime.

Mr Assad has vowed to recapture the whole of Syria and keep "fighting terrorism".

Turkey's relations with fellow mainly Sunni Muslim power Saudi Arabia have warmed considerably in recent months.

Ties had been damaged by Saudi's role in the 2013 ousting of Egyptian president Mohamed Morsi, a close ally of Ankara.

In December, President Recep Tayyip Erdogan visited Riyadh for talks with King Salman as well as key decision-makers crown prince Mohammed bin Nayef and deputy crown prince Mohammed bin Salman.

Meanwhile, Turkey has also been tightening relations with Qatar, another key opponent of Mr Assad in the Syria conflict.

Mr Erdogan on Friday held several hours of talks in Istanbul with Qatar's Emir Sheikh Tamim bin Hamad al-Thani, the presidency said, but the contents of the talks were not revealed.

AFP/Reuters