A few relevant quotes:
"Since 2009, Amnesty International has stopped publishing estimates on the use of the death penalty in China, where data on the use of the death penalty is considered a state secret. The lack of reliable data does not allow Amnesty International to publish credible minimum figures for the use of the death penalty in the country; however, available information strongly indicates that China carries out more executions than the rest of the world combined."
"Where “+” appears after a figure next to the name of a country – for instance, Yemen (13+) – it means that this is the minimum figure calculated by Amnesty International. Where “+” appears after a country name without a figure – for instance, death sentences in Myanmar: (+) – it means that there were executions or death sentences (more than one) in that country but insufficient information to provide a credible minimum figure. When calculating global and regional totals, “+” has been counted as 2, including for China."
"Official figures on the use of the death penalty were available only in a small number of countries. In Belarus, China and Viet Nam, data on the use of the death penalty continued to be classified as a state secret. Little or no information was available in some countries - in particular Egypt, Eritrea, Malaysia, North Korea and Syria, due to restrictive state practice and/or political instability. It is possible that judicial executions did in fact take place in Syria, but none could be confirmed for the present report."
"In North Korea death sentences are often imposed even though the alleged crime is not subject to a death sentence under domestic law."
For extended discussion of China, see pages 19 to 21.
"While reliable reports indicate that at least 70 executions were carried out in North Korea, Amnesty International believes the true figure to be much higher. Further reports about numerous public executions and executions of political opponents of North Korea’s leader Kim Jong-un, including his uncle Jang Seong-taek, were also recorded, but such information could not be independently verified. Other crimes for which people were reportedly executed included murder and cannibalism, embezzlement, pornography, escaping to China, corruption, activities that countered the goals of the Korean Workers' Party and watching banned videos from South Korea."
More information on North Korea can be found on page 25.