Activists detained after Israel intercepted a Gaza-bound aid flotilla have begun describing what they say was violent treatment during their detention, including beatings, taser use and physical intimidation.

Several passengers said Israeli forces stormed the vessel before forcing activists to the ground, striking detainees and using electric tasers during the raid. Some former detainees also alleged they were denied proper medical treatment and subjected to aggressive interrogations after being taken into custody.

The flotilla had been attempting to deliver humanitarian aid to Gaza and draw attention to worsening conditions inside the territory. Organisers said those aboard included medical workers, international activists and pro-Palestinian campaigners participating in what they described as a peaceful mission.

Former detainees said the treatment continued after the interception, with some alleging they were verbally abused, threatened and held in harsh conditions before later being released or deported. Human rights advocates and pro-Palestinian groups condemned the reported treatment, accusing Israeli forces of using excessive force against unarmed civilians attempting to deliver aid.

The incident has renewed international attention on Israel’s blockade of Gaza and the risks faced by activists attempting to reach the territory by sea.