Catholic leaders and charities in the Philippines have condemned as "very barbaric" President Rodrigo Duterte's plan to restore the death penalty and execute "five or six" criminals each day despite what is widely acknowledged to be a corrupt legal system.

Duterte, 71, has made reviving the death penalty in the mainly Catholic nation his top legislative priority as part of a brutal war on crime that has killed 5,300 people, according to the Daily Nation.

"There was death penalty before but nothing happened. Return that to me and I would do it every day: five or six [criminals]. That's for real," he said on Saturday.

An official at the Catholic Bishops' Conference of the Philippines said the Church "totally opposed" Duterte's plan. "The Philippines will be viewed as very barbaric," Father Jerome Secillano, the executive secretary at its public affairs office, told AFP. "It's going to make the Philippines the capital of death penalty in the world."

The Philippines abolished the death penalty in 2006 after strong opposition to capital punishment from the Catholic Church, to which 80 per cent of Filipinos belong.

Before taking office in June this year, Duterte vowed to introduce executions by hanging, saying he did not want to waste bullets and adding that he believed snapping the spinal cord was more humane than a firing squad.

Duterte said that he viewed the death penalty not as a means to deter crime but for retribution.

A vote is due in the House of Representatives in January.

The United Nations' human rights chief, Zeid Ra'ad Al Hussein, said in a letter to the Philippines congress this month that reviving capital punishment would violate the country's international obligations.

Nonetheless, on Saturday Duterte insisted executions were necessary to fight the drug scourge which he said was "destroying" the nation.

Although his aides have attempted to dismiss his incendiary statements as hyperbole, human rights advocates expressed alarm at Duterte's remarks.

"Setting a quota for executions is just too much. One death is too much because we are talking about lives," Amnesty International Philippines vice chairman Romeo Cabarde told AFP.

Catholic leaders and activists have urged the government instead to reform a slow and corrupt justice system which they said was likely to send innocent people to death row.

Secillano added that bishops planned to persuade lawmakers against voting for the death penalty and would attend congressional debates next month.