(Adds comments from U.N. human rights chief's spokesman)
BAGHDAD, Jan 21 (Reuters) - Iraq has hanged 26 people convicted of "terrorism" offences, the Justice Ministry said on Tuesday, pursuing what a U.N. official criticised as a "conveyor-belt of executions".
All those executed on Sunday were Iraqi nationals. Among them was Adel al-Mashhadani, a "Sahwa" militia leader in Baghdad who was "famous for sectarian crimes", Justice Minister Hassan al-Shimari said in a statement on the ministry's website.
Sahwa (Awakening) militias are formed mostly of Sunni Muslim tribesmen who helped U.S. troops roll back an al Qaeda-led insurgency in Iraq from 2006 onwards.
Violence in Iraq has surged in the past year to its highest levels since the Sunni-Shi'ite sectarian bloodshed that peaked in 2006 and 2007 when tens of thousands of people were killed.
Iraq hanged at least 151 people in 2013, up from 129 in 2012 and 68 in 2011, New York-based Human Rights Watch said in its annual world report published on Tuesday.
The United Nations human rights chief, Navi Pillay, has frequently condemned Iraq's mass executions.
"This continued conveyor-belt of executions by the government of Iraq is simply deplorable," her spokesman, Rupert Colville, said of Sunday's hangings.
"Iraq's justice system still has huge deficiencies which mean that resorting to even a small number of executions is risking a grave and irredeemable miscarriage of justice," he said. "When people are executed by the dozen, it means that such miscarriages of justice are virtually certain to be occurring." (Reporting by Raheem Salman; Writing by Alistair Lyon)