The Syrian army had said earlier that six people were killed in the strike on the base - the first time that the U.S. has directly attacked the government of President Bashar al-Assad.
A U.S. missile strike targeting an airbase in central Syria killed nine civilians, including four children, on Friday, state news agency SANA reported.
The Syrian Arab News Agency, which is monitored by President Assad's Ministry of Information, claims that nine civilians were killed even though the airbase was attacked at 3.45am local time.
U.S. President Donald Trump said he had ordered missile strikes against the airfield from which a deadly chemical attack was launched, declaring he acted in America's "national security interest" against Syrian President Bashar al-Assad.
The state TV called the attack an "American aggression".
The attack targeted the Shayrat military base in the central Homs province, the source told Xinhua. Syrian officials and their allies also said they did not expect the attack to lead to an expansion of the conflict.
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He did not specify where the planes had been moved to or who had warned the Syrian government.
It came in response to a suspected chemical attack on a rebel-held town on Tuesday widely blamed on the Damascus regime, which has repeatedly denied it has used toxic substances.
Nasr al-Hariri, chief negotiator of the High Negotiations Committee (HNC), said on Twitter that the strikes "should they continue, would kick off a correct start in combating terrorism".
"We hope for the continuation of the strikes in order to prevent the regime from using its planes to launch any new air raids or going back to using internationally banned weapons", said Ahmad Ramadan, head of the media office of the Syrian National Coalition political opposition group.
Global reaction to the USA cruise missile attack on a Syrian airbase has exposed the stark lines by which the worldwide community is divided over the six-year civil war. Saudi Arabia called it a "courageous decision" by Trump, while Israel said the United States president had sent a "strong and clear message".