WASHINGTON - U.S. President Donald Trump said early Friday the United States was closely monitoring an attack in a casino in Manila.

"We’re closely monitoring the situation ... but it is really very sad as to what’s going on in the world with terror," Trump said at a White House ceremony where he announced the United States would withdraw from a landmark 2015 global agreement to fight climate change.

"Our thoughts and our prayers are with all of those affected,” Trump added.

Gunshots rang out from the Resorts World Manila entertainment complex in Pasay City early on Friday, with an armed man setting fire to casino tables inside the complex.

A spokeswoman for the U.S. State Department said it was not aware of any U.S. citizens affected, but was continuing to gather information.

"We remain in close contact with local officials," she said, adding that U.S. citizens were advised to exercise caution and monitor local media for further information.

However, Philippine National Police Director General Ronald dela Rosa downplayed initial claims that it was a terrorist attack.

He told reporters that the gunman tried to steal casino chips and had not killed anyone.

"We cannot connect this yet to terrorism," he told reporters.

He said the attack could be robbery-related. - with a report from Reuters