Dutch Foreign Minister Bert Koenders has said the only way to halt the flow of migrants pouring into Europe is to end the war in Syria, advising the European Union to hold talks with Lebanese officials.

Koenders, who visited a refugee camp in the eastern Bekaa Valley on Tuesday, said: "It is not only a question of border controls and quotas. If the war in Syria does not end, people will keep coming."

Two new sites north of Syria's Latakia airport could be preparing to receive Russian forces, specialist defense publication IHS Jane's Intelligence Review said on Tuesday citing satellite imagery.

At the Istamo weapons storage complex and the al-Sanobar military complex "preparations appear to be under way to introduce Russian forces," said Robert Munks, editor of the London-based publication.

Coalition forces carried out an air strike in Iraq that killed a senior leader of the Islamic State group, the Pentagon said Tuesday, also confirming the death in Syria of a French jihadist.

Abu Bakr al-Turkmani died September 10 in a strike in Tal Afar in northern Iraq, Pentagon press secretary Peter Cook told reporters. 

Russia has increased its deployment of warplanes to Syria but so far they appear to be positioned to defend their own base rather than to mount an offensive campaign, U.S. Secretary of State John Kerry said Tuesday.

"Yes, they have increased aircraft and there are certain kinds of aircraft there which, depending on what Russia's decision is about its long-term intentions, could raise questions," Kerry said.

Former CIA chief and retired general David Petraeus on Tuesday said America should take a more active role in the Syrian crisis, including implementing no-fly zones to prevent regime planes dropping barrel bombs.

Speaking before the Senate Armed Services Committee, Petraeus said the U.S.-led coalition fighting the Islamic State group had made "inadequate" progress in Iraq and Syria and said the Syrian civil was a "geopolitical Chernobyl." 

The U.N.'s envoy on Syria, Staffan de Mistura, held meetings this week aimed at reviving peace talks, a statement said Tuesday, amid mounting pressure to end the four-year war. 

After several attempts to find a political solution, De Mistura in July proposed a fresh approach whereby Syrians would take part in "thematic" working groups.

The U.N. refugee chief called Tuesday for European states to show solidarity in their response to the continent's worst migration crisis since World War II, ahead of emergency EU talks.

"There is no way to resolve a crisis of this dimension if each country acts alone and based solely on its own interests," United Nations High Commissioner for Refugees Antonio Guterres told Portuguese broadcaster RTP.

Russia has delivered new arms including warplanes to Syria as the regime increases attacks on jihadists, officials said Tuesday, in a sign that Moscow's growing support for its ally is having an effect.

A senior Syrian military official told AFP Damascus had received a fresh batch of arms, including at least five fighter planes, while a monitoring group said there had been a marked increase in regime attacks on the Islamic State group.

Israeli Prime Minister Benjamin Netanyahu and Russian President Vladimir Putin have agreed on a plan to avoid "misunderstandings" in Syria amid an apparent military build-up by Moscow to support President Bashar Assad.

The two leaders reached an agreement on Monday during talks in Russia, with Israeli media reporting that the discussions involved avoiding clashes between the two militaries' jets over Syria.

German intelligence warned Tuesday that the number of Islamic extremists in the country had increased sharply in recent months and expressed serious concern that they were recruiting among refugees.

The Office for the Protection of the Constitution (BfV), Germany's domestic security watchdog, said the number of radical Salafists had surged to 7,900 in September from 7,500 in June, and that many were trying to lure asylum-seekers into their ranks.