The UN's Syria envoy on Wednesday urged the presidents of Russia and Turkey to find an "immediate diplomatic solution" to the conflict in northwestern Syria, where both powers are militarily active.  

"I am sure you all join me in urging them to find an immediate diplomatic solution that could spare civilians further suffering... and create more conducive conditions for a political process", UN special envoy for Syria Geir Pedersen told Arab League foreign ministers in Cairo.    

Turkish President Recep Tayyip Erdogan, who backs some rebel groups in Syria's Idlib Province, and Russian President Vladimir Putin, a supporter of the Syrian government led by President Bashar al-Assad, are due to meet in Moscow on Thursday.  

Since December, the Syrian government has led a deadly military campaign against rebels in Idlib, the last major opposition stronghold in the country's northwest after nearly nine years of civil war. Tensions have soared further since Ankara launched its own offensive days ago against Syrian government forces, after more than 50 Turkish soldiers were killed in Idlib Province in recent weeks. 

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Pedersen called the direct clashes between Syrian government and Turkish forces "a worrying change in the nature of the conflict."  

Despite being on opposite sides of the war, Ankara and Moscow have kept lines of negotiation open. Erdogan has said he hopes a ceasefire will be "swiftly established" when the two meet.  

Pedersen warned that "with five international armies active inside Syria, the dangers of wider international conflagration remain."  

A "meaningful political process" is needed to avoid "a bleak and uncertain future, with dire regional consequences," Pedersen added.  

"The path out of war to peace is plainly very difficult. There is very little trust and confidence to move forward, and not enough political will to do so," he said.  

Close to one million people have been displaced due to the recent conflicts.

Russia is racing to reinforce its troops in Syria by sea and air before Putin's talks with Erdogan, flight data and shipping movements show. 

A Reuters analysis of flight data and correspondents' monitoring of shipping in the Bosphorus Strait in northwestern Turkey shows Russia began to step up naval and airborne deliveries to Syria on February 28, the day after 34 Turkish soldiers were killed in an airstrike in Syria. 

That incident prompted concern in Moscow that Turkey might close the Bosphorus to Russian warships and bar Russian military transport planes from using Turkish air space. 

The Russian Defense Ministry did not immediately respond to a request for comment. A Turkish official, who asked not to be identified, said there was no plan to close the strait, which would force Russia to take longer routes to Syria. 

But Russia appears to be reinforcing Syria at its fastest rate since October, when U.S. forces withdrew from some parts of Syria and Moscow scrambled to fill the vacuum.

Reuters' monitoring of the Bosphorus since February 28 shows Russia has sent five warships towards Syria within six days. That exceeds a usual pattern of one or two warships per week. 

The Russian military announced the departure of the Admiral Grigorovich and Admiral Makarov frigates for Syria, but three other warships have followed unannounced. One is the Orsk, a landing ship capable of carrying 20 tanks, 50 trucks or 45 armored personnel carriers and up to 400 troops. The others – the Novocherkassk and the Caesar Kunikov - are landing ships that can carry over 300 troops, tanks and armor. 

Turkey has responded by beefing up its escort protocol for Russian warships using the Bosphorus. Three Turkish patrol boats and a helicopter escorted the Russian frigates – such ships are usually accompanied by a single coast guard vessel. 

(With input from AFP, Reuters)