Isis has claimed responsibility for a series of attacks on Western targets since 12 people were killed in an attack on the headquarters of the Charlie Hebdo satirical weekly magazine in Paris last January.
In recent weeks attackers acting alone have targeted individuals and groups in Europe, the most recent being an attack at the weekend by a machete-wielding Algerian shot dead by police after injuring two female officers.
The change in approach has coincided with campaigns against Isis in its strongholds in Iraq and Syria.
The Miss World beauty pageant was last held in the Philippines in 1994.
The event is expected to attract a lot of attention next year after Wurtzbach was crowned in extraordinary scenes at the contest in December last year. The host, Steve Harvey, announced Ariadna Gutierrez Arevalo, Miss Colombia, as the winner - and then realised he had read the card incorrectly. The crown was taken off Arevalo's head and placed on Wurtzbach's.
The threat from Isis has been growing in the Philippines. Abu Sayyaf, an insurgent group fighting for a hardline Islamist state in the southern Philippines, has pledged allegiance to Isis.
Two Canadians were murdered by the group earlier this year.
Abu Sayyaf has its roots in the longstanding Islamist insurgency in the southern islands of the predominantly Roman Catholic Philippines, and has focused its operations on lucrative banditry. The faction - a loose alliance of splinter groups - has survived the deployment of US special forces "advisers" as part of George W Bush's "war on terror" and a series of offensives by the poorly-equipped Philippine army.
The West under attack
The list of attacks on Western targets claimed by or blamed on Isis (Islamic State) continues to grow:
August 6 Machete attack in Belgium: A 33-year-old Algerian attacks two policewomen with a machete before being shot dead by a third officer.
July 26 French priest killed: Attackers slit an elderly priest's throat.
July 24 German suicide blast: A failed Syrian asylum-seeker blows himself up outside a music festival.
July 18 German train attack: A 17-year-old asylum-seeker attacks passengers with an axe.
July 14 Nice lorry attack: A 31-year-old Tunisian rams a 19-tonne truck into people celebrating Bastille Day in Nice.
June 28 Istanbul airport attack: A triple suicide attack at Istanbul's Ataturk airport kills 47 people.
June 13 French police couple killed: A man stabs a police officer to death before slitting his partner's throat.
June 12 Orlando gay bar shooting: A gunman kills 49 people.
March 22 Brussels attacks: Suicide attacks kill 32 people and wound more than 340 at airport and metro station.
January 12 Tourists die in Istanbul: Twelve Germans killed in a suicide attack.
December 2, 2015 San Bernardino shooting: Husband and wife kill 14 people.
November 13 Paris attacks: Co-ordinated suicide attacks kill 130 people and wound more than 350.
October 31 Russian jet bombed: Passenger jet crashes in the Sinai desert after a bomb rips a hole in the plane, killing all 224 people on board.
June 26 Tunisia beach attack: Gunmen kill 38 people at a beach hotel in Sousse. Three months earlier 22 were killed in an attack on a museum in Tunis.
January 7-8 Paris shootings: Gunman kills a policewoman before attacking a Jewish supermarket where he kills four people before being killed by police.
January 7 Charlie Hebdo attack: Brothers kill 12 people at the headquarters of the satirical weekly magazine in Paris.
- AFP
