ISLAMABAD — Human rights groups expressed concern over the fast pace with which Pakistani authorities are executing death row prisoners, as the total number of executions for the year reached at least 135 this week, higher than for any full year in a decade.

Human Rights Commission of Pakistan, an independent group, estimated that 135 executions had taken place in a little more than five months since the lifting of a moratorium on the death penalty in December. However, Reprieve, a Britain-based nonprofit group, has estimated the number to be 150.

The Pakistani government does not release official figures on executions, and the numbers given out by rights activists are usually based on newspaper reports.

“Pakistan is racing to become one of the world’s most prolific executors — overtaking even Saudi Arabia and the U.S.,” said Maya Foa, head of the death penalty team at Reprieve, in a statement.