The long and passionate kiss between the two young men continued for several seconds, as onlookers gawped and photographers snapped incessantly. Their lips finally parted when police officers yanked one man away and shoved him into a waiting police car.

Uninhibited public shows of affection between men are seldom seen in Italy. But these two weren't lovers. And the show they put on outside Naples police headquarters on Wednesday evening was something rarer still – a full kiss on the lips between Camorra mobsters as a powerful sign, made very public, that the bonds of the crime syndicate would remain strong and the arrested man would remain silent. Experts say that this particular mob tradition has never previously been filmed or photographed.

The young mobster under arrest, Daniele D'Agnese, 27, a senior figure in the notorious Scissionisti clan of the Camorra, locked lips with not one but two younger male associates in front of press cameras and crowds. La Stampa newspaper said the kisses were a message telling the pair that they would not be left to fend for themselves.

"It was a sign to the weaker members of the group telling them, 'We'll continue to be a group; we'll command the same territory and whatever happens, you won't be abandoned'," it said. The kiss may also have been a sign to rival clans that Scissionisti bonds remained strong.

Other newspapers suggested that with the display, D'Agnese – seized yesterday along with senior boss, Carmine Amato, in a remote hideout outside Naples – was telling those watching that he would not talk while in custody. Dr Corrado de Rosa, a psychiatrist and expert witness in mafia trials, who wrote the book I Medici della Camorra (The Doctors of the Camorra), told The Independent that the kisses could have meant any number of things, but he tended to veer toward the latter explanation.

"I think it's possible that D'Agnese was telling the two – and all the people watching – that he was going to keep his mouth closed and not tell the authorities anything," he said. "I have heard of Camorristi kissing each other on the lips like this but I don't think I've ever heard of it being done in public before. That it was done this way shows the kisses were designed to carry a very important message."

Dr de Rosa added that the kisses were interesting for another reason: they demonstrated the huge difference between the less disciplined, "anything goes" Camorra and Sicily's conservative Cosa Nostra.

"Such a thing is inconceivable between Cosa Nostra members. The Sicilian mafia is extremely homophobic. But the Camorra is much more liberal and modern in that respect. Camorristi aren't bothered how they are portrayed or what other people think. As long as they're able to function and carrying on making money." He said their laissez-faire attitude was evident when, in February 2009, police arrested the 27-year-old transsexual Ugo "Ketty" Gabriele on suspicion of being a Camorra drug smuggler.

D'Agnese, who is thought to be the deputy chief of the clan and senior body guard of Amato, 30, was found with his wife and children when police swooped on their refuge in the hills above Naples on Wednesday morning. Amato, arrested in the same raid, was listed as one of Italy's 100 most dangerous fugitives, and was wanted for murder, drug trafficking and mafia association. He had been on the run since 2009.

One of the police officers outside the Naples court yesterday, who did not want to be named, told La Repubblica that he was not that surprised by the scene. "Similar things happen with the Camorra in the eastern parts of the city, that is Barra, Ponticelli. San Giovanni and Teduccio," he said. And he added that for the Scissionisti clan, "a kiss on the lips between men is a real tradition".

He also had some observations on the attire of both mobsters after their arrests. D'Agnese and his shaven- headed boss Amato could not look more different. But both were wearing James Dean T-shirts. "I can imagine the boss chose that type of T-shirt for himself and then took one for his bodyguard, the officer said. "This is something else we often see; the same brand, the same label of shoes. It's a real passion for mob bosses." Earlier evidence that James Dean T-shirts are the Scissionisti clan uniform came a few months ago when another senior clam member, Cesare Pagano, was seized wearing one.

Clan loyalties among Camorra members are very strong; mobsters are prepared to die for them – and often do. The worst big feud in recent years – over control of the Scampia zone of the city, which involved the Scissionisti group – resulted in more than 60 murders between 2004 and 2005. The violence prompted widespread public revulsion against the Camorra and led to a big crackdown by the authorities.

Mafia rituals

* For Italy's oldest and best-known mafia group, Cosa Nostra, a kiss can mean very different things depending on where it's planted.

* A kiss on the mouth from a Cosa Nostra mobster is a sign that you're going to be killed. But a kiss on the cheek indicates that the Cosa Nostra member regards you as an equal. Kissing a mobster on the hand is a sign of subservience, and a way of keeping a mob boss happy.