# Investigation into Movimento 17 ottobre in Milan

> Live situation record from CLSTR: https://clstr.news/situations/investigation-into-movimento-17-ottobre-in-milan
> Updated: 2026-10-26T19:02:00.000Z. Sources: 132. Developments: 3.

Authorities in Milan have arrested Youssef Siher, a 30-year-old researcher and journalist, on charges including terrorism, incitement to commit crimes with terrorist intent, and organized violence. Prosecutors allege Siher is the leader of ‘Movimento 17 ottobre’, a social media and Telegram-based group that emerged following violent protests and looting in Milan on October 17 and 18.

Investigators claim Siher used digital platforms to coordinate mass mobilizations and promote an eversive project designed to cause social instability. Interior Minister Matteo Piantedosi confirmed that police intercepted digital communications containing instructional manuals for violent protesters. Prosecutors allege Siher utilized his technical expertise to develop a ‘revolutionary strategy’ through digital tools, managing a Telegram group that has grown to approximately 11,000 members.

Siher’s wife, Sagia Hammoud, is also under investigation for her alleged role in co-administering the movement’s online channels. The case has ignited significant political debate. Maurizio Acerbo, secretary of Rifondazione Comunista, defended Siher’s right to freedom of opinion, while a former professor of Siher described the media coverage as a ‘shameful media smear campaign’.

Franco Gabrielli, former head of the Italian Police and founder of the ‘Più uno’ movement, has addressed the arrest. Gabrielli stated it is legitimate to question whether Siher, due to his non-moderate positions, was under prior surveillance. He emphasized the need for the judiciary to determine if the movement represents an isolated event or a broader threat to national security, while stressing the importance of not discrediting institutions during the investigation.

## Claims

- Youssef Siher is accused of incitement to commit crimes with the aggravating factor of terrorism. (corroborated by 3 sources)
- Siher is alleged to be the administrator of the 'Movimento 17 ottobre' social media channels. (corroborated by 3 sources)
- Youssef Siher has been detained by authorities. (corroborated by 3 sources)
- The so-called ‘October 17 Movement’ is currently under judicial investigation. (corroborated by 3 sources)
- Franco Gabrielli questioned if Siher was under prior surveillance. (corroborated by 3 sources)
- Maurizio Acerbo defended Siher's right to freedom of opinion. (corroborated by 2 sources)
- Maurizio Acerbo stated that he and his party do not support Hamas. (corroborated by 2 sources)
- Senator Filippo Sensi criticized the political stance taken regarding Siher. (corroborated by 2 sources)
- The social media group managed by Siher reached nearly 9,000 followers. (single source)
- The prosecution has requested pretrial detention in prison for Siher. (single source)
- Investigators believe Siher's technical skills allowed for a 'revolutionary strategy'. (single source)

## Timeline

### 2026-10-26: Franco Gabrielli addresses arrest of Youssef Siher

Former Police Chief Franco Gabrielli calls for investigation into Youssef Siher's role in the ‘Movimento 17 ottobre’ following civil unrest and his arrest in Italy.

13 sources. https://clstr.news/cluster/franco-gabrielli-addresses-arrest-of-youssef-siher

### 2026-10-26: Youssef Siher faces terrorism charges in Milan investigation

Milan prosecutors seek prison time for Youssef Siher, accused of leading the ‘Movimento 17 ottobre’ and using social media to incite terrorism and organized violence following unrest in Milan.

17 sources. https://clstr.news/cluster/youssef-siher-faces-terrorism-charges-in-milan-investigation

### 2026-10-24: Youssef Siher arrested in Milan on terrorism and incitement charges

Milan prosecutors have arrested researcher Youssef Siher, accused of terrorism and incitement for allegedly leading the ‘Movimento 17 ottobre’ digital network following violent protests in Milan.

123 sources. https://clstr.news/cluster/crema-police-dismantle-hate-group-planning-violent-patrols

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Cite as: Investigation into Movimento 17 ottobre in Milan. CLSTR, https://clstr.news/situations/investigation-into-movimento-17-ottobre-in-milan