A concert by pop icon Britney Spears in Manila went ahead last night, amid extraordinary measures taken by police to head off a terrorist attack as government troops battled Muslim radicals holed up in the southern city of Marawi for a fourth week.

About 200 policemen patrolled the venue, many in anti-riot gear, in the hours leading up to the concert.

Armed guards and special units with bomb-sniffing dogs were also deployed at parking areas and entrances.

Backpacks were banned and concertgoers were advised to be at the venue two hours before the start of the concert to avoid long queues resulting from thorough inspections.

Said metropolitan Manila police chief Oscar Albayalde: "We could not take this for granted.

"We really had to prepare with all that is happening not only here in the Philippines, but all over the world."

Before the concert, police and emergency responders conducted a security run-through from where concert-goers queued and entered the concert ground .

Said concert organiser Paul Aquino: "The ratio was one security official for every 42 concertgoers."

The preparations came in the wake of a bomb attack during the concert of pop star Ariana Grande in Manchester that killed 22 people and fears that the battle in Marawi could inspire lone-wolf attacks in the capital.

Police were also concerned after an attempt by a frustrated gambler to rob and torch a casino in Manila recently left 38 people dead.

Up to 10,000 people attended yesterday's concert, police said.

Raul Dancel