The family of an Australian man being held in Israeli detention says their son was mistreated during his arrest.
Sydney man Michael Coleman was detained aboard a flotilla that was intercepted on its way to Gaza.
Israel claims that the takeover was peaceful, but the activists report being tasered and shackled.
Free Gaza Australia spokeswoman Kate Ausburn says Michael Coleman called his father John from Israel last night and told him how he was treated.
"Michael told his father that when the soldiers boarded the boat he was personally assaulted and thrown around, had his arm twisted up behind his back," she told the ABC.
John Coleman has more details.
"One of the gentlemen on board, David Heap, was tasered. The rest of them were in some cases quiet badly knocked around," Mr Coleman told SBS.
"When they arrived in Ashdod they refused to leave the ship and again they were man handled off the ship in quite a violent manner".
Two months ago, a UN report on a flotilla raid in 2010 accused the Jewish state of acting with excessive force.
On that occasion commandos fatally shot nine protesters on board the Turkish Mavi Marmara.
"That report made clear that there are some legal rights that Israel can exercise but there are also some clear limits on the ability to use force in these types of interdictions," Professor of International Law Don Rothwell told SBS.
Israel says its blockade is necessary to prevent weapons from entering the coastal territory.
The Free Gaza Movement in Australia is calling on the government to intervene.
"It is about time that Julia Gillard or Kevin Rudd picked up the phone and called prime Minister Benjamin Netanyahu and demanded that Michael Coleman be unconditionally released from prison," Free Gaza spokesman James Godfrey told SBS.
Israel has charged Michael Coleman, along with 20 fellow activists under immigration laws, and is expected to deport them within 72 hours.
