Syrian President Bashar al-Assad said Sunday that his coalition with Russia, Iran and Iraq must succeed in Syria's war, suggesting the alternative would be a region in chaos.

The alliance "must succeed, otherwise we are facing the destruction of the entire region and not just one or two states," Mr. Assad said in the Islamic Republic of Iran News Network interview.

It was his first public comment since Moscow began airstrikes in Syria in support of his regime last week. Mr. Assad praised Russia, saying it had the vision and fortitude to defeat rebel forces seeking to topple him.

Late last month, Russia announced an intelligence-sharing agreement with the Syrian regime, Iran and Iraq. The deal laid the groundwork for Moscow to begin strikes last Wednesday against opponents of Mr. Assad.

The Syrian president said Russia and his country had a long-standing relationship.

Unlike the West, the Russians "have never tried to impose anything on us throughout the history of this relation, particularly during this crisis," he said.

A time frame of Russia's involvement hasn't been set, he said, and its military presence depends on how events unfold. A Russian official last week said Moscow's campaign in Syria could last three to four months.

Russia's growing role in Syria comes as a U.S.-led coalition continues to carry out airstrikes there against Islamic State militants who took over large parts of the country last year. While Russia backs Mr. Assad, the U.S. backs rebel groups challenging his rule. Both however are fighting Islamic State.

Mr. Assad also praised the involvement of his allies Iran and Iraq. Iran has strengthened its presence on the ground recently through its proxy forces.

China hasn't taken part in the conflict militarily, Mr. Assad added. But it "supports the Russian role and the Russian efforts," including its presence in Syria, he said.

Mr. Assad used the interview to blast the U.S.-led coalition that has been fighting Islamic State by air in Syria and Iraq since last fall, saying it had been ineffective in fighting terrorism.

He also railed against the West's handling of the Syrian refugee crisis, which has seen more than 4 million flee the country. He said Western countries bore the responsibility as they have supported terrorism in Syria.

Asked whether he would manage Syria's crisis differently if he could return to the start of the conflict in 2011, he said that the past 4½ years had been a lesson.

"Every national crisis is a very rich lesson to the officials, to the population and to society in general," he said.

Meanwhile, Russian military officials said its air force was stepping up strikes against targets in Syria, as warplanes carried out dozens more sorties during the weekend, again hitting areas controlled by other opponents of Mr. Assad's regime as well as Islamic State.

Col. Gen. Andrei Kartapolov from the Russian armed forces' General Staff said the strikes on "terrorists" had "considerably reduced their combat potential."

"Panic and desertion has started among them. About 600 mercenaries have left their positions and are trying to flee to Europe," he told reporters Saturday.

The Russian Defense Ministry said in a statement Sunday that its aircraft flew 20 sorties in the past 24 hours, attacking 10 Islamic State positions. Aircraft carried out 20 flights against nine targets from late Friday through Saturday, the ministry said.

A concrete-piercing bomb destroyed a command center and an ammunition center near the Islamic State stronghold of Raqqa, according to the ministry.

Tactical bombers eliminated storage centers for military hardware, munitions depots and a training camp in Idlib province, the ministry said.

"The airstrikes have disrupted the control and logistic support of the terrorist organization, and seriously damaged the infrastructure used for preparation for acts of violence on Syrian territory," the ministry said.

Col. Gen. Kartapolov said that Russia had "issued notification" of the start of its air operation before strikes began on Wednesday, including informing the U.S. military attaché in Iraq. "Foreign colleagues...were recommended to withdraw all instructors and advisers as well as those people who were trained with American taxpayers' money," he said.

James Marson in Moscow contributed to this article.

Write to Asa Fitch at asa.fitch@wsj.com and Sam Dagher at sam.dagher@wsj.com

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(END) Dow Jones Newswires

October 04, 2015 20:55 ET (00:55 GMT)