Saudi Arabia is executing people at a “frightening” rate, campaigners have warned, after it emerged the kingdom had killed its 70th prisoner of the year bringing the total number to almost half that of 2015.

Alaa al-Zahrani, who was put to death in the Red Sea city of Jeddah, was found guilty of killing fellow Saudi Abdullah al-Sumairi with a rock to the head, the interior ministry revealed in a statement published by the Saudi’s official state news agency SPA.

Several advocacy groups that monitor the death penalty worldwide placed the figure at 157 last year, with beheadings reaching their highest level in two decades.

Saudi Arabia does not release annual tallies, though it does announce individual executions in state media throughout the year. Most people beheaded in the oil-rich kingdom are beheaded by sword.

Speaking to The Independent, Amnesty International UK’s Head of Policy and Government Affairs Allan Hogarth said: “The death penalty is always cruel and unnecessary, but the Saudi justice system lacks evens the basics of a fair trial system and it’s truly frightening that its courts are sentencing so many people to death.

With death sentences imposed after deeply unfair – and sometimes secret – proceedings, with defendants often denied a lawyer, and with courts regularly convicting people on the basis of ‘confessions’ extracted under torture, Saudi Arabia is making a mockery of justice and dozens of people are paying with their lives.

“It’s time that ‘strategic allies’ like the UK started speaking out about this shocking state of affairs. For too long Downing Street has bent over backwards to avoid ‘offending’ the Saudi royals. Saudi Arabia’s human rights record is utterly appalling and the UK government should say so.”

The kingdom came under intense criticism at the beginning of the year when it executed 47 people for “terrorism offences” in one day, including the prominent Shia cleric Sheikh Nimr al-Nimr.