Resorts World Manila (RWM) have said they are currently on lockdown following reports of gunfire from unidentified men.
A masked gunman was on the second floor of one hotel, firing at guests, hotel employees fleeing the scene told CNN Philippines.
Masked men dressed in black have stormed the resort with long guns (rifles).
Heavily-armed SWAT officers wearing bullet proof vests and body armor also descended on the scene.
It was not immediately clear how many people may have been injured or killed.
The company is working with the Philippine National Police to keep all guests and employees safe.
In a tweet, RWM said: “We ask for your prayers during these difficult times.”
Police, fire trucks and SWAT teams were called to the area, near Manila airport.
Gunfire and explosions were reported at the hotel sometime after midnight Friday local time. Metropolitan Manila Development Authority reported that there is a “fire alert” at the Resort World Manila in Pasay about 12:30 a.m. local time.
The U.S. Department of State Bureau of Consular Affairs confirmed there were reports of explosions and gunfire at the resort and urged people to avoid the area.
Police and emergency crew are at the scene.