Saudi Arabia's King Salman opened a summit of Arab leaders on Sunday by condemning an old foe, Iran, without making any reference to missile strikes by Western powers on Syrian government targets over a suspected gas attack a week ago.

Regional powerhouses Saudi Arabia and Iran have been locked in a decades-long struggle for supremacy that is being waged in proxy wars in several countries, including Yemen and Syria.

"We renew our strong condemnation of terrorist acts carried out by Iran in the Arab region, and we reject its blatant interference in the internal affairs of Arab countries," King Salman said in the eastern Saudi city of Dhahran, without giving specifics. Iran denies the charges.

There was no mention in King Salman's remarks nor in the summit's closing statement of Saturday's missile launch by the United States, Britain and France against three alleged chemical weapons facilities in Syria.

The Syrian government denies using - or possessing - chemical weapons and said the strikes were an act of aggression.

Saudi Arabia and allies expressed support for the strikes on Saturday, but Iraq and Lebanon have condemned them.

Other countries like Jordan and Kuwait refrained from taking a position, instead renewing calls for a political solution to the multi-sided war which has killed at least half a million people in the past seven years.

Military help over the past three years from Russia and Iran, which also backs Lebanon's Hezbollah group and Shia Muslim militias in Iraq, has allowed Syrian President Bashar al-Assad to crush the rebel threat to topple him.

Russian President Vladimir Putin proposed cooperating with the Arab League on regional security, specifically in Iraq and Syria following the defeat of Islamic State militants there, according to Russian news agencies.