Italian authorities have arrested more than 20 secessionists, including a former MP, on suspicion of terrorism and possessing weapons of war as part of a plan to separate the region of Veneto from the rest of Italy.
Italian police said the group had turned a bulldozer into a war tank and planned to use it in a violent attack on St Mark's Square in Venice.
The incident is reminiscent of a more than seven-hour takeover of the piazza's bell tower by secessionists in 1997, who proclaimed an independent, if short-lived, Venetian republic.
Police said 24 people have been arrested, including Franco Rocchetta, a former member of parliament for the Northern League, on suspicion of terrorism, subversion of the democratic order and possessing weapons of war. In addition, 27 others are being investigated.
Emotions in the wealthy northern region of Veneto have been running high in the wake of a self-styled online referendum calling for independence, coinciding with the annexation of Crimea. According to the online poll, 89 per cent of respondents voted for Veneto to break away from Italy.
The Northern League said it will march on Sunday in the city of Verona to protest against the "unjust" arrests and a new immigration bill which would decriminalise and soften the rules on illegal immigration.
Northern League Senate leader Massimo Bitonci said: "We call on the Venetians and all those who can no longer bear the intolerable oppression of the central state to fly the flag of St Mark from their homes to show their solidarity with the Venetians and Lombards who have been unjustly imprisoned."