MANILA (UPDATED) - The gunman behind the attack at Resorts World Manila in Pasay City has killed himself, police said on Friday.

"Our assessment is he burned himself. He committed suicide," Oscar Albayalde, chief of the Manila police office, said in a radio interview.

Gunfire shook the resort casino around midnight Friday as the attacker fired multiple shots and burned casino tables.

Eyewitnesses initially said that gunmen were wearing masks and black shirts, but Philippine National Police (PNP) Chief Ronald Dela Rosa later said there was only one gunman involved.

"It is too early to tell if this is a terror attack. Based on the facts we gathered... there was an absence of violence dahil the lone gunman did not shoot an innocent person," Dela Rosa said.

The police chief said they are also looking at robbery as an angle since the gunman "ransacked (a) storage room of casino chips" and placed about P113 million worth of chips inside a backpack.

Authorities earlier said the gunman was likely "addicted to gambling" who "went crazy."

Closed-circuit television footage showed the gunman carried a long firearm, which resembled a "baby Armalite" or a small version of the M-16 assault rifle, police said.

"At least 30 people were brought to nearby hospitals for immediate medical attention," the management of Resorts World Manila said in a statement.

The casino resort's officials declined to release the victims' names as immediate family members have yet to be informed of their conditions.