WASHINGTON (Reuters) - U.S. President Donald Trump said on Thursday the United States was closely monitoring what he described as a "terrorist" attack in Manila, while the police chief of the Philippines said the shooting incident at a gaming resort may have been a robbery.

"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.

The Philippines' police chief said on Friday there was no indication the shooting incident at a Manila gaming resort was related to terrorism and it may have been a robbery.

Ronald dela Rosa said police were in control of the situation and it was possible Islamic State would claim responsibility to serve its propaganda.

He told DZMM radio that a lone gunman entered the gaming area at Resorts World and set some tables on fire. The gunshots, he said, were not aimed at people in the room.

"We cannot say this is an act of terror ... he did not hurt anyone," he said. "If you are a terrorist you will sow terror."

Gun shots and explosions rang out from the resort early on Friday and local media reported armed men were inside. Resorts World Manila said on social media it was in lockdown and the local fire department said a blaze was burning on the second floor of one building.

A spokeswoman for the U.S. State Department said earlier it was not aware of any U.S. citizens being 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.

(Reporting by Eric Walsh and David Brunnstrom; Editing by Peter Cooney and James Dalgleish)