Masked gunmen are besieging the Resorts World Manila casino in the Philippines, in what early media reports are describing as a likely terrorist attack.

According to Interaksyon.com, an unspecified number of heavily armed men wearing black clothes and face masks opened fire at the Travellers International-owned casino shortly after midnight Thursday local time.

Explosions were also reportedly heard at the scene and thick smoke has been observed coming out of the building. A casino employee told DZMM Teleradyo that one of the gunmen had spread flammable liquid on some casino tables.

The gunmen reportedly began their assault on the property’s second floor, where the bulk of the casino’s gaming operations are located. Witnesses reported seeing gunmen searching the third floor, which houses many of the property’s VIP gambling rooms.