Israeli Prime Minister Benjamin Netanyahu will visit Russia for talks with President Vladimir Putin, officials said Saturday, amid concerns Moscow may be about to deliver advanced missiles to Syria.

Putin's spokesman Dmitry Peskov confirmed the visit to AFP, but declined to give details, although he told the Interfax news agency it was being planned for next week.

The state RIA Novosti news agency, citing a diplomatic source, also said Netanyahu expected to call on Putin at his Black Sea residence in Sochi early next week.

"The visit is currently at the stage of active preparations," the source was quoted as saying.

Israeli officials told AFP on condition of anonymity that the two leaders would meet "soon" but did not elaborate.

"Netanyahu and Putin will discuss the Russian arms sales to Syria, in particular the sale of advanced S-300 anti-aircraft missile systems," Israel's Haaretz newspaper reported Friday, adding that the Israeli premier would also seek to raise the Iranian nuclear issue.

Israel twice last week carried out air strikes near Damascus, attacks a senior Israeli source said were aimed at preventing the transfer of sophisticated weapons to Hezbollah, the powerful Lebanese Shiite group allied to Syria.

The Wall Street Journal reported on Wednesday that Israel had provided information to Washington about the imminent sale to Syria of Russian S-300 missile batteries, advanced ground-to-air weapons that can take out aircraft or guided missiles.

British Prime Minister David Cameron visited Putin in Sochi on Friday to talk strategy on the Syria conflict, days after the US and Russian foreign ministers agreed to work together on a solution.

US Secretary of State John Kerry has warned that any such sale would be "potentially destabilising" for the region.

Russia however refuses to rule out supplying weapons to Syria, saying it has to honour existing contracts.

On a visit to Warsaw on Friday, Foreign Minister Sergei Lavrov said Moscow was continuing to fulfil contracts by delivering military hardware to President Bashar al-Assad's regime in defiance of calls for a freeze.

"Russia has sold and signed contracts a long time ago, and is completing supplies of the equipment, which is anti-aircraft systems, according to the already signed contracts," he told reporters.

A high-ranking diplomatic source, who participated in the Putin-Cameron talks, said the issue of arms supplies to Syria had been raised at their meeting.

Speaking to Russian news agencies, he insisted Moscow had to meet its obligations.

"Everything is clear here: there is no embargo on supplies, and we are implementing contracts signed earlier, that is we are fulfilling obligations we have taken upon ourselves," the source was quoted as saying.

"Any weapons that are being supplied (to Syria) in accordance with earlier contracts, are purely defensive in nature."

The West and Russia have been repeatedly at odds over the Syria conflict, with the United States and Europe accusing Moscow of seeking to prop up Assad and selling him arms.

The war in Syria has cost an estimated 70,000 lives and displaced millions of people, including hundreds of thousands who have fled to neighbouring countries.

Earlier this week Lavrov and Kerry proposed holding a new peace conference but the diplomatic source, said there were too many disagreements over its format and who should attend.