A British journalist detained by Greek police for entering Olympic facilities on a security expose boasted on Friday how she wandered round "with extraordinary ease" for several hours before being spotted.

"It was supposed to be one of the most secure places in the world, impenetrable to terrorists plotting a possible attack on this summer's Olympics," Laura Peek wrote in a front-page Times article under a photo of herself in a floodlit stadium.

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"But for two-and-a-half hours... The Times was able to wander, unnoticed and unchallenged, inside what is supposed to be the Olympic ring of steel."

In a tactic popular with British media, reporter Peek and a Times photographer were seeking to show up lax security when they were detained in the early hours of Thursday.

Three German journalists were also held.

Already stung by a barrage of international criticism despite spending 1 billion euros ($1.18 billion) on security, Greek authorities were angry.

"I would tell journalists to treat Olympic security very seriously and not see it as just an opportunity for a story," Public Order Minister George Voulgarakis said on Thursday.

"GUARD GAVE ME BEER"

The Times' operation came just hours before one bomb exploded and another device was discovered outside banks in Athens, further heightening jitters about safety at the August games following a triple explosion last week.

The Times journalist said her tour of the main stadium began when she asked a security guard if she could look around.

"Instead of ordering me to leave, the guard handed me a beer and showed me around... Astonishingly, he warned me in broken English to watch out for police officers who patrolled every 25 minutes.

"After a Times photographer took more than 90 pictures of what was intended to be a secure area, I walked into the middle of the Olympic arena. It was only then -- standing in the full glare of floodlights mounted on the famous Calatrava roof arches -- that we were spotted by a policeman."

Peek described having stood in a tunnel under the stadium.

"I waited in the tunnel for 50 minutes to see if I would be picked up by a patrol. A policeman shone in his torch three times but did not spot me," she said. "In that time, I could have planted anything from a home-made bomb to an alarm clock to a device on a long-term timer."

When a policeman finally confronted the Times pair, he asked if anyone had challenged them. "When we shook our heads, he shrugged and smiled," she said.

The journalists only received a ticking-off.

"In the early hours of the morning, the local chief of police arrived. After giving us a formal caution, he admitted: 'The stadium is 50-50 secure but we still have three months to go... This time last year you would not have been stopped.'"