TRIESTE, Italy, Oct 18 (Reuters) - Italian police used water cannon and tear gas on Monday in an attempt to clear a sit-in at the port of Trieste, where opponents of the government"s mandatory COVID-19 health pass have tried to block access. The northeastern port has been the focal point of protest in Italy over the introduction of new rules last Friday that require all workers either to show proof of vaccination, a negative coronavirus test or recent recovery from infection. Police in full riot gear moved in on Monday morning after several hundred dock workers disrupted access to one of the main gates at Italy"s largest commercial port. The crowds were pushed aside by jets of water followed by volleys of tear gas. Many of them headed towards the city"s main square to continue their protest in front of government offices. "They attacked us. I am speechless. I never expected it," said Stefano Puzzer, the spokesman of the port protesters. "We will sit down here. We are keeping calm. We will not give up." Port workers demonstrate outside the entrance of the major port of Trieste, as Italian riot police try to disperse the protest which has taken place for several days against the implementation of the coronavirus disease (COVID-19) health pass, the Green Pass, in the workplace, in Trieste, Italy, October 18, 2021. REUTERS/Borut Zivulovic Italian riot police try to disperse a protest of port workers outside the entrance of the major port of Trieste, which has taken place for several days against the implementation of the coronavirus disease (COVID-19) health pass, the Green Pass, in the workplace, in Trieste, Italy, October 18, 2021. REUTERS/Borut Zivulovic People demonstrate at the Unity of Italy Square (Piazza Unita d"Italia), as Italian riot police try to disperse the protest which has taken place for several days against the implementation of the coronavirus disease (COVID-19) health pass, the Green Pass, in the workplace, in Trieste, Italy, October 18, 2021. REUTERS/Borut Zivulovic 1/5 Italian riot police try to disperse a protest of port workers outside the entrance of the major port of Trieste, which has taken place for several days against the implementation of the coronavirus disease (COVID-19) health pass, the Green Pass, in the workplace, in Trieste, Italy, October 18, 2021. REUTERS/Borut Zivulovic The protesters refused to disperse despite repeated police use of water cannons into the evening, TV footage showed. Three police officers were slightly injured in clashes, Italian media reported. The government says the mandatory health "Green Pass" is needed to keep workers safe and to encourage more people to get vaccinated. Under the rule, effective until year-end, workers will be suspended without pay and face a fine of up to 1,500 euros ($1,730) if they try to work without the certificate. Most Italians support the provision, opinion polls show, but a vocal minority says it impinges on core labour rights. Some 15% of private and 8% of public sector workers have no Green Pass, according to a government document seen by Reuters last week. However, Puzzer has said around 40% of Trieste"s port workers are not inoculated. Vaccine hostility is also higher in the city than in most of Italy, with an "anti-vax" party taking 4.5% of the vote at mayoral elections this month.