There was a worrying rise in executions in 2021 as Covid-19 restrictions were eased, Amnesty International says, with spikes seen in Iran and Saudi Arabia.

A report by the human rights group says at least 579 executions were known to have been carried out in 18 countries - a 20% increase on the previous year.

Iran accounted for the biggest portion of this rise. It put to death at least 314 people, compared with 246 in 2020.

Saudi Arabia more than doubled its number of executions to 65.

The global total is the second-lowest figure, after 2020, that Amnesty has recorded since at least 2010.

However, as in previous years it does not include China. Although it is believed to execute thousands of people each year, the data on its use of the death penalty is a state secret.

Amnesty says secrecy also made it impossible to verify reports from North Korea and Vietnam, where an extensive number of executions is thought to have taken place.

Amnesty's annual death penalty report says Iran's highest known figure since 2017 was due in part to a more than five-fold increase in drug-related executions to 132, from 23 in 2020.

The rights group calls this a "flagrant violation of international law, which prohibits use of the death penalty for crimes other than those involving intentional killing".

The 140% rise in the number of executions in Saudi Arabia last year was, according to Amnesty, the start of a "grim trend that continued in 2022 with the execution of 81 people in a single day in March".

Significant increases were also recorded in Somalia (21, up from 11 in 2021), South Sudan (9, up from 2) and Yemen (14, up from 5).

The report says that the easing of Covid-related restrictions also led to judges handing down at least 2,052 death sentences in 56 countries - an almost 40% increase on 2020.

It highlights an "alarming" rise in the use of the death penalty under martial law in Myanmar, where the military transferred the authority to try civilian cases to military tribunals.

"Instead of building on the opportunities presented by hiatuses in 2020, a minority of states demonstrated a troubling enthusiasm to choose the death penalty over effective solutions to crime, showing a callous disregard for the right to life even amid urgent and ongoing global human rights crises," said Agnès Callamard, Amnesty's secretary general.