Several armed men robbed a bank in broad daylight in Naples, holding 25 people hostage before making their escape via a tunnel.

Police surrounded a branch of Crédit Agricole in the southern Italian city shortly after the robbery began around midday local time (10:00 GMT).

Local outlets reported that they negotiated with the robbers before the hostages could be released, about two hours into the robbery.

Firemen could be seen smashing in a window with battering rams and helping people climb out from inside in videos shared on social media.

Some hostages simply shook off the shards of glass and walked on.

But others looked visibly shaken, crying and hugging their relatives. Six people, who were in a state of shock, were offered medical assistance.

One man later told local news site Fanpage.it that the robbers had locked them into a room and that, while they were armed, "they did not use violence".

Nobody was seriously injured. "Thanks to the swift response... all the hostages were freed shortly after 13:30 without serious injuries," regional official Michele di Bari said in a statement.

A large crowd of bystanders, local residents and firefighters gathered in the square waiting for developments, while ten of thousands of people tuned into a livestream from the scene of the crime.

Members of the special forces of the carabinieri armed police were urgently flown in from Tuscany.

It was not until several hours later that they stormed the bank by breaking a window.

Several shots and the loud noises of stun grenades could be heard on the live feed shortly after.

But by then, the robbers had reportedly escaped through a tunnel, local media reported. It was thought they could have vanished into the sewer system.

The video feed later showed a number of carabinieri and firefighters peering into a manhole nearby as a crowd continued to mill about the square.

Fanpage.it reported that it was not yet possibly to quantify the value of the loot taken because the robbers had seized personal safety deposit boxes rather than cash.