On Friday, at least 36 people were killed when a gunman burst into a casino.
He fled with more than 2 million U.S. dollars (£1.5 million) in stolen casino chips, then forced his way into a room in an adjoining hotel and killed himself.
Manila police chief Oscar Albayalde told reporters that it was "a simple robbery and most likely it was done by a demented person".
"Islamic State fighters carried out the Manila attack in the Philippines", the militant group's Amaq news agency said. The only gunshot wound was a guard at the complex, who accidentally shot himself when the suspect entered the room, authorities said.
"He would have shot all the people gambling" if his goal was terrorism, said national police chief Ronald dela Rosa.
Philippine authorities have said they suspect the man was trying to rob the casino and that there was no evidence it was a terrorist attack.
He also set gaming tables on fire and filled a backpack with gambling chips worth 113m Philippine pesos (£1.7m, $2.3m). Dela Rosa described him as "white, with a mustache" and about 6 feet tall. He lay down on the bed, covered himself with a blanket, doused himself with gasoline and then set himself on fire, dela Rosa said.
Dozens of police trucks and several huge Special Action Force vans and armored personnel carriers lined side streets near the hotel, casino and shopping mall complex as the drama unfolded.
The gunman fled with $2 million in stolen casino chips, then forced his way into a room in an adjoining hotel and killed himself.
Manila's main global airport closed the gates of its four main terminals for two hours while the attack at the nearby Resorts World was happening and had implemented extra security measures, airport authorities said.
The ministry said the South Korean victim suffered an apparent heart attack while resting after the evacuation early Friday.
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Resorts World Chief Operating officer Stephen Reilly said the gunman was dressed in combat gear and fired a number of shots as he entered the building.
Hours later, when company officials announced the names of employees who perished in the attack, Hazel Anne was first on the list of 23 employees. But Dela Rosa says the assailant did not fire at people he met.
"We took out a ladder to save them".
The attacker walked straight into the building, past a lone security guard who panicked when she saw the suspect's automatic rifle, Albayalde said.
"We believe that our security (measures) were enough, they will be reviewed", Reilly said when asked whether arrangements were adequate.
As news of the attack had spread, President Donald Trump offered the thoughts and prayers of the American people to the Philippines. "I could not carry her".
Maintenance worker Ronald Romualdo told DZMM he saw a woman fall from an upper floor while trying to escape.
"It is really very sad as to what's going on throughout the world with terror", he said from the White House Rose Garden.
The Philippines has been on heightened alert amid a crisis in the south of the country, where troops have been battling Islamist rebels since May.
Security was tightened around the presidential palace on Friday, with armored personal carriers stationed on approach roads and river ferries barred from passing close by.
This story has been corrected to show the currency conversion on the value of the stolen chips to be more than $2 million, not $200,000.