Polish police have detained 135 people and investigated more than 300 suspected criminal incidents as part of a nationwide security operation launched after a series of violent attacks at schools last week. Police said on Monday that officers had inspected nearly 80,000 educational institutions since Friday, recording 311 incidents involving suspected criminal offenses. “Police operations aimed at ensuring the safety of children, young people and all employees of educational institutions are continuing across Poland. Officers are monitoring the internet around the clock and responding to every report,” the police said in a statement. The security crackdown follows three attacks with bladed weapons at schools in Poland’s Mazovia region last week that left one person dead and 14 others injured, raising fears of further violence and a possible online challenge encouraging copycat attacks. However, Interior Minister Marcin Kierwiński said on Sunday that investigators had so far found “no links whatsoever” between the incidents, with no evidence that those involved had been in contact with one another. Prime Minister Donald Tusk also ruled out the involvement of a large, organized group, warning instead of a growing “fascination with violence” among young people, particularly online. Gdańsk schools under ‘BRAVO alert’ In the northern port city of Gdańsk, police officers are visiting every school on Monday, while police and municipal guards have stepped up patrols around educational institutions. Gdańsk Mayor Aleksandra Dulkiewicz said access to schools and kindergartens was being strictly controlled, with only students and staff allowed inside under Poland’s BRAVO alert level, the second tier of its four-stage terrorism warning system. “We ask parents and guardians to exercise caution and check whether their children are bringing dangerous objects to school,” city authorities said. “In the current situation, no ‘stupid joke’ will be ignored and such behavior could have very serious consequences,” they added. Schools are also increasing teacher supervision during breaks, while psychological support is available to students and education staff. Similar security measures are being introduced in other parts of Poland’s northern Pomerania region.