By Frances Harrison BBC correspondent in Colombo

Italy has long been a destination for immigrants from Sri Lanka

Police officers said the whole operation only took a couple of hours but they netted 166 young men from India, Pakistan and Bangladesh whom they suspect are illegal immigrants.

They were acting on a tip off.

In the last month alone Sri Lankan police have arrested nearly 700 South Asians in part of a crack down on human smuggling.

They say the tropical island has become the major transit point for catching illegal boats to Europe especially since visa restrictions for people from neighbouring countries have been eased.

"These people were coming to try for Italy and Greece," says Inspector Thurairatnam Jayaratnam of the Mount Lavinia police intelligence unit who organised the raid.

"They think there's less security here, so they are using Sri Lanka as a transit point," he says adding that this started in earnest about a year ago.

Paying a 'fee'

All people gave four or five thousand dollars Detained Pakistani

One man, who did not want to give his name, admitted in front of the police that he had paid $4,000 to an agent to take a boat to Greece where his brother works.

"All people gave four or five thousand dollars," he says causing shrieks of outrage from other detainees who deny they were involved.

"I didn't pay in Pakistan" he explains.

"I was going to pay the fee in Greece when I got there."

The police say this man gave them the name of the agent who is the real kingpin they are keen to catch.

"Actually we have to make use of these victims to track down the big shots who make the money by forging passports and bringing these people here," explains Inspector Jayaratnam.

"We have to put a full stop to this," he says, though many policemen express sympathy for the detainees saying they are just poor people who want a better life in Europe.

No hard proof

They should know - many Sri Lankans have also made the dangerous journey by fishing trawler across the high seas to Egypt, Greece or Eastern Europe.

The problem for the police is proving that all the people they detained on Thursday were planning to break the law.

Only 26 had no passports and six had overstayed their visa.

The rest had valid documents.

Police officers say it is suspicious that so many single young men should be staying together though they all say they are tourists or businessmen.

"I was sleeping in the hotel and in the early morning there was a knock on door; it was the police and they came and took my passport," complains a Pakistani man.

"They said you are going to Italy. I am not - I am businessman," he insists.

"Maybe some 30 people were going to Italy but not us," he says and starts brandishing dollars bills to show he has money and was not relying on any shadowy middleman to pay his hotel bill.

Then everyone pulls out currency - Pakistani and Indian rupees, Sri Lankan rupees and US dollars - in an attempt to prove their innocence.

Imitiaz Gul from Gujarat in Pakistan said he had come to buy ceiling fans for his uncle's shop back home and had been caught up by accident in the raid.

"My passport has disappeared - one of my friends took it - but I have a ticket," says another Pakistani man in some visible distress.

The police ask him how he managed to buy an airline ticket without a passport.