ATHENS (AFP) - The Beijing Games flame is handed over to China on Sunday in a tightly-guarded Athens ceremony with Greek authorities fearing a repetition of anti-Chinese protests that have dogged the seven-day Olympic torch relay through Greece.

Greek police have imposed unprecedented security with 2,000 officers on patrol around the city as sporadic protests by pro-Tibetan activists and Greek leftists were rising along the flame's passage.

Tight restrictions were also imposed on media coverage of the torch relay as it entered Athens' legendary Acropolis on Saturday while the final Sunday run through Athens was cut short hours before the flame's delivery to Chinese officials.

"We have changed the programme," Hellenic Olympic Committee spokesman Tassos Papachristou told AFP.

"The flame will now run a small distance through the centre of Athens before (the handover ceremony) at 3:00 pm (1200 GMT)," he said.

Sporadic protests have erupted along the torch relay route through Greece this past week.

They began on March 24 in ancient Olympia with three members of press freedom group Reporters Without Borders (RSF) disrupting the flame-lighting ceremony, one of them unfurling a banner with the Olympic rings replaced by handcuffs behind top Games organiser Liu Qi as he spoke.

Breaching a massive security cordon around the small town, a group of Tibetan activists also staged a street protest in Olympia shortly after.

Protesters also tried to demonstrate later in the week as the flame entered the Greek cities of Salonika and Volos but were prevented to do so by police.

Police stopped 20 demonstrators putting up a banner in Volos, central Greece, arresting one person, while about 10 Danish activists were also blocked around 70 kilometres (45 miles) outside the neighbouring city of Larissa.

Greek leftists were prevented from raising a banner in Athens Saturday

China has come under increasing international pressure over its crackdown on protesters in the Tibetan capital Lhasa and Chinese provinces bordering the Himalayan region.

Tibetan activist groups have put the death toll from weeks of unrest at 135-140 Tibetans. China says rioters killed 18 civilians and two police officers.

At a press conference on Saturday, the general secretary of the Beijing Games organising committee Wang Wei insisted the unrest was "orchestrated".

"People have not been given the truth...the truth is that the turmoil, the riots, were orchestrated by a small group of people," Wei said, adding that any violence against monks took place in protests outside China's borders.

"If some small minority...a super minority want to demonstrate this is their problem, it is not the Olympians' problem," said Hellenic Olympic Committee chairman Minos Kyriakou.

As the flame entered Athens on Saturday, a few dozen members of Tibetan human rights groups and Falungong -- a spiritual movement outlawed in China -- staged a peaceful protest beneath the Acropolis against the Chinese clampdown in Tibet and the holding of the Olympics in Beijing in August.

Media were banned from the Acropolis during the flame's arrival Saturday.

"Our intention is not to stop people from demonstrating but to avoid having an incident that disrupts the torch relay," said HOC spokesman Papachristou.

A police convoy and a dedicated guard of runners has accompanied the flame on its seven-day trek through Greece.

A crowd of around 20,000 people is expected later Sunday at the formal handover at Athens' all-marble Panathinaiko Stadium, where the first modern Olympics were held in 1896.

Spectators will be searched on entry and all banners, signs or objects that could be thrown will be confiscated, police said.

The torch's journey to Beijing is the longest ever, lasting 130 days and covering 137,000 kilometres (85,000 miles) worldwide. Most of it will be on Chinese soil.