The family of a political activist who died in the custody of Palestinian security forces last month have accused the Palestinian Authority of trying to cover up his death.

       Relatives of Nizar Banat said that they had still not received a document stating an official cause of death, and that the authority had made efforts to settle the matter out of court.

       “The behaviour of the Palestinian Authority until this moment is criminal behaviour, covering up a crime,” Ghassan Banat, Nizar’s brother, told reporters.

       Nizar Banat was an outspoken critic of the authority who called on western nations to stop providing aid to the governing body on account of its human rights violations and growing authoritarianism.

       In a series of posts and live videos on Facebook, Mr Banat had criticised the authority’s close security coordination with Israel, which is seen by many Palestinians as betrayal, and its corruption. He had also lashed out at president Mahmoud Abbas in April for calling off what would have been the first Palestinian elections in 15 years. Mr Banat was a candidate on an opposition slate.

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       His family said security forces stormed into Mr Banat’s bedroom while he was sleeping, and beat him, inflicting bloody head wounds, before removing him from the house. He died shortly afterwards while in custody.

       His death has prompted weeks of protests. On 5 July at least six activists were arrested by security forces while protesting outside the Palestinian Authority headquarters. Multiple witnesses said the police used pepper spray and beat the protesters with batons.

       The authority, seen as a crucial partner of the US and other western countries, formed a committee to investigate Mr Banat’s death. His brother said that weeks later, the family has heard little from the government.

       ‘‘Until this moment, we have failed to obtain a death certificate. How can you have a citizen who dies without issuing a death certificate?” Ghassan Banat said.

       Accompanied by two family lawyers, the brother rejected what he said were attempts by the authority to use tribal elders to intercede in order to close the case and stop it from reaching the courts.

       “This file will not be resolved or closed through elders or tribal ways,” he said. “Nizar’s [case] is a political assassination and will remain open until justice is achieved, even if it takes 1,000 years.”

       The Palestinian Authority is widely viewed as corrupt and authoritarian, with a poll last month showing that support for Mr Abbas, who took power for what was supposed to be a four-year term in 2005, had nosedived.

       Mr Abbas has faced mounting pressure after calling off the elections when it appeared that his Fatah party would suffer a crushing defeat to the rival Hamas militant group.

       Last month, Palestinian security forces arrested prominent activist and critic Issa Amro after he used Facebook to criticise recent arrests.