A UK publisher has condemned an attack by masked men in Gaza on a Palestinian writer and political figure, Atef Abu Saif, accusing the assailants of deliberately breaking his fingers.

Comma Press, a not-for-profit publisher that worked with Abu Saif, said that the beating on Monday night had almost killed him.

“He was hospitalised with a broken leg, broken arm, fractured skull, and lacerations to his face and upper body. Most notably, the assailants broke his fingers in right arm – a recognised punishment for writers,” Ra Page, founder of Comma Press, said in an email.

“We’re all shocked and appalled by this turn of events,” he added.

No group has claimed responsibility for the assault, which happened during the peak of several days of protest in Gaza against tax hikes by its rulers, Hamas, whose forces have been accused of violently suppressing the rallies.

Although activists say their demands are purely economic, Hamas has accused its Palestinian political rival, Fatah, of fomenting strife. Abu Saif has worked for Fatah as a spokesperson for more than a year, but Hamas denies it sent men to beat him.

Author of The Drone Eats with Me, a diary of the 2014 war between Hamas and Israel, Abu Saif is also a frequent opinion writer, with articles in the Guardian and the New York Times.

On Thursday, he was moved by ambulance to a hospital in the West Bank city of Ramallah and was in a stable condition. Speaking to Palestinian media from his hospital bed, his head wrapped in bandages, Abu Saif denied that Fatah has pushed for protests: “These masses went out to look for a better life.”

A member of his family, speaking on condition of anonymity, said he believed Hamas orchestrated the attack after Abu Saif’s recent criticism of their crackdown.

Dozens of demonstrators have been clubbed by riot police and arrested at the rallies. Amnesty International said its Gaza-based researcher, Hind Khoudary, had been questioned by interrogators who threatened to prosecute her for spying.

One youth activist who took part in the protests, Alam Abusafia, 25, had not been heard from since Wednesday when he was detained, according to his brother, Jayyab, who lives in the UK. “We’ve been trying every single backchannel to get any news about him or just give him one minute to speak to my mum,” he said. “He’s just someone who is very angry about the tax Hamas imposed on the people of Gaza.”

Hamas runs Gaza while its political adversary, the Palestinian Authority that is dominated by the Fatah party, has limited autonomy over the Israeli-occupied West Bank. Israel separates the two territories. Hamas and Fatah factions fought a near-civil war in 2007.

The Palestinian Authority did not directly blame Hamas for Abu Saif’s beating, but said in a statement that “the assault committed by a criminal gang … reflects the worsening situation caused by the dark division”.