A new annual report on the death penalty calls sub-Saharan Africa a "beacon of hope" amid a decline in executions worldwide.Twenty countries across sub-Saharan Africa have now abolished the death penalty for all crimes, Amnesty International says in the report released early Thursday. Just two countries in the region, Somalia and South Sudan, carried out executions last year.Executions worldwide dropped again in 2017, with at least 993 recorded in 23 countries. That's down 4% from the year before and down 39% from 2015.At least 2 591 death sentences were recorded in 53 countries last year, down from a record high of 3 117 the year before, the London-based human rights organization said.The numbers don't include the thousands of executions and death sentences that Amnesty International believes have occurred in China, where they are considered a state secret.China remained the "world's top executioner, the report said. Excluding China, 84% of the reported executions last year were carried out in Iran, Saudi Arabia, Iraq and Pakistan. Countries resuming executions in 2017 were Bahrain, Jordan, Kuwait and the United Arab Emirates.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and FacebookThe United States remained the only country in the Americas to carry out executions, with 23 last year, up slightly from the year before.With the progress in Africa, "the isolation of the world's remaining executing countries could not be starker," said the organization's secretary general, Salil Shetty.Even among those countries some "significant steps" were seen. In Iran, executions were down 11 percent and drug-related executions were reduced to 40%. In Malaysia, changes to anti-drug laws now allow discretion in sentencing for drug trafficking crimes.But Amnesty International called "distressing" the continued use of the death penalty for drug-related offences, with 15 countries last year imposing death sentences or carrying out executions. Drug-related executions were recorded in China, Iran, Singapore and Saudi Arabia, where "drug-related beheadings rocketed from 16% of total executions in 2016 to 40 percent in 2017."The rights group also expressed concern that at least five people in Iran were executed last year for crimes committed when they were under the age of 18, with another 80 people with similar pasts still on death row.People with "mental or intellectual disabilities" were executed or faced a death sentence in the United States, Japan, Pakistan, Singapore and the Maldives.Worldwide at least 21 919 people are known to be under a death sentence, Amnesty International said: "Now is not the time to let up the pressure."Other challenges remain, the report says, including in sub-Saharan Africa: Both Botswana and Sudan reportedly resumed executions this year.And early this year, Uganda's president Yoweri Museveni said he will sign the first death warrants in nearly two decades to create fear among criminals, vowing to "hang a few".