Yasin Bulbul, Associated Press
Turkey's President Recep Tayyip Erdogan addresses his supporters during a rally in the southern province of Hatay, Turkey, which borders Syria, Friday, April 7, 2017. Erdogan says the U.S. missile strike on a Syrian air base is a "concrete step" but argues that it's not enough.

BEIRUT — Turkey described the U.S. missile attack on an air base as a "cosmetic intervention" unless it removes President Bashar Assad from power, while the Syrian leader's strong ally Iran called Saturday for the formation of an international fact-finding committee to investigate the chemical weapons attack in a northern Syrian town that killed scores of people and trigged the American attack.

The statements by Assad's opponents and backers came as warplanes struck the northern Syrian town of Khan Sheikhoun where the chemical attack killed 87 people earlier this week. The air raid killed a woman and wounded her son, according to the Britain-based Syrian Observatory for Human Rights and the Local Coordination Committees.

Iranian president Hassan Rouhani called for the formation of an international fact-finding committee to investigate the chemical weapons attack. State television reported Rouhani's statement quoting him as insisting that the committee must be impartial and "must not be headed by Americans."

Rouhani said that "neutral countries should come and assess to make it clear where the chemical weapons came from."

Iran is one of Assad's strongest backers sine the country's crisis began six years ago leaving some 400,000 people dead, half the country's population displaced and more than five million as refugees in neighboring countries.

The chemical attack on Khan Sheikhoun on Tuesday triggered a U.S. missile attack two days later that struck a Syrian air base in central Syria with 59 missiles, killing nine people.

Syria's government denied it carried out any chemical attack on Khan Sheikhoun, and Russia's Defense Ministry said the toxic agents were released when a Syrian airstrike hit a rebel chemical weapons arsenal and munitions factory on the town's eastern outskirts.

Turkey's Foreign Minister Mevlut Cavusoglu said Ankara sees the U.S. intervention in Syria as appropriate but not enough.

"If this intervention is limited only to an air base, if it does not continue and if we don't remove the regime from heading Syria, then this would remain a cosmetic intervention," said Cavusoglu in the southern city of Antalya.

Cavusoglu, whose country is a strong backer of the Syrian opposition, said the most ideal process will be a political solution that leads to a transitional government accepted by all Syrians as soon as possible. He said that for that "this oppressive Assad needs to go."

Cavusoglu said after the transitional government takes over, it will be followed with elections in which Syrians in the country and abroad can vote.

British Foreign Secretary Boris Johnson canceled a planned trip to Russia because of fast-moving events in Syria. Johnson said Saturday the situation in Syria has changed "fundamentally" following a chemical weapons attack on civilians and a U.S. missile strike on a Syrian airfield.

Johnson condemned Russia's continued defense of Assad "even after the chemical weapons attack on innocent civilians."

He had planned to travel to Russia Monday on a trip intended to start fresh dialogue with the Russian government.

U.S. Secretary of State Rex Tillerson plans meet with G-7 foreign ministers in Europe next week before going on to Moscow. Johnson says Tillerson will be able to give a "clear and coordinated message to the Russians."

In the capital Damascus, dozens of Syrian students gathered outside the offices of the United Nations to protest the U.S. missile attack.

The protesters held banners and chanted anti-American slogans Saturday such as "Death to America" and "Death to Israel."

One of the banners they carried read: "The Iraqi scenario will not be repeated in Syria." They were referring to the 2003 U.S.-led invasion of Iraq after Washington accused Saddam Hussein of hiding weapons of mass destruction — a belief that later turned out to be incorrect.

University student Ashraf Fadel said he came to denounce "the unjust American aggression against Syria." He added that the United Nations was "created to support America instead of serving the wronged people."

Elsewhere in Syria, a pair of activist groups reported that a U.S.-led coalition airstrike hit a boat carrying civilians fleeing across the Euphrates River, killing seven members of the same family. The groups Raqqa is Being Slaughtered Silently and Sound and Picture reported that the attack killed a woman and her six children. The attack occurred in the Shuaib al-Zeker area near where U.S.-backed Syrian fighters have been on the offensive against IS under the cover of coalition airstrikes.

In Saudi Arabia, the official Saudi Press Agency reported that U.S. President Donald Trump has spoken by telephone with King Salman about the U.S. missile strike on Syria.

The news agency reported that during the Friday phone call, the Saudi monarch congratulated Trump for his "courageous decision."

Saudi Arabia said the missile launch by Trump was the right response to "the crimes of this regime to its people in light of the failure of the international community to stop it."

The kingdom is among the most vehement opponents of Assad and supports Sunni rebel groups fighting to oust him. The Sunni rulers of Saudi Arabia are in a power struggle for regional dominance with Iran's Shiite government and view Tehran's support of Assad as a threat to the region.

Associated Press writers Aya Batrawy in Dubai, United Arab Emirates, Zeynep Bilginsoy in Istanbul and Albert Aji in Damascus, Syria contributed to this report.