Pentagon chief Chuck Hagel has castigated the U.S. strategy in Syria in a memo to the White House, saying Washington must explain its intentions toward President Bashar al-Assad's regime.

The memo was sent last week to President Barack Obama's national security adviser, Susan Rice, a defense official said Thursday, confirming a New York Times report.

U.N. peace envoy Staffan de Mistura proposed Thursday to set up so-called "freeze zones" in war-torn Syria to suspend fighting in some areas and allow humanitarian aid to be delivered.

De Mistura told reporters after meeting with the U.N. Security Council that he did not have a peace plan but rather "an action plan" to ease suffering from the more than three-year war in Syria.

The Free Syrian Army (FSA) already has 400 fighters in Kobane and more are on the way, the commander of a unit there said in a rare public appearance Thursday.

Nizar al-Khatib, who said he was in charge of an FSA unit sent into Kobane, told reporters in Istanbul that a command post had been set up to coordinate activities between his forces and the Kurdish fighters also battling Islamic State (IS) jihadists for the town.

Syria accused Turkey on Thursday of a "flagrant violation" of its sovereignty, as Ankara allowed Iraqi Kurdish peshmerga fighters and opposition rebels to cross its border to battle jihadists.

"Once again, Turkey has shown its conspiratorial role... by allowing foreign forces and terrorist groups to enter Syria," said a foreign ministry statement reported by state television.

Heavily armed Iraqi peshmerga forces reached the Turkish border Thursday and a first group entered the town of Kobane as they prepared to join fellow Kurds battling the Islamic State group.

The group of 10 fighters were to coordinate with local Kurdish militia who have been holding off an assault by IS jihadists for six weeks, a monitoring group said.

The army said on Thursday that it has arrested a Lebanese man who admitted to smuggling arms to jihadists taking position on the Lebanese-Syrian border as the military rounded up dozens in its clampdown on militants.

Abdullah Mahmoud al-Hujairi was apprehended in the area of Wadi Hmeid in the northeastern border town of Arsal, said an army communique.

Gunmen, who engaged in deadly battles with the Lebanese army in the northern coastal city of Tripoli and in Akkar over the weekend, deserted their positions and fled the scene after they realized that they will not be able to stand firm against the army, As Safir newspaper reported on Thursday.

According to the daily, gunmen linked to fugitives Shadi al-Mwalawi and Ousama Mansour in Tripoli's al-Tabbaneh neighborhood decided to leave their position after Mawlawi posted a voice record accusing Muslim scholars of “abandoning them.”

Hizbullah is more dangerous than militant groups operating in the Gaza Strip, an Israeli army general said, expressing belief that the party has dug tunnels across the border from Lebanon in preparation for any future war with the Jewish State.

As a result of the greater threat from Hizbullah and in the event of a future conflict, the Israeli army will have to take “many more decisive acts and employ much more power” than it did in Gaza, Maj.-Gen. Yair Golan, commander of Israeli forces on the Lebanese and Syrian fronts, told Army Radio on Wednesday.

U.N. Special Coordinator for Lebanon Derek Plumbly ruled out the naturalization of Syrian refugees, denying international pressure to keep the displaced in Lebanon.

In remarks to As Safir daily published on Thursday, Plumbly said: “The issue of the naturalization of the Syrian refugees is out of the question.”

Australia on Thursday passed a law criminalizing travel to terror hotspots, a tough counter-terrorism measure aimed at stopping jihadists from going to Iraq and Syria to fight.

The Australian government has been increasingly concerned about the flow of foreign fighters to the Middle East to join militant groups such as Islamic State, with 70 Australians believed to have already made the journey.