Pakistani military courts have sentenced seven people to death over attacks including an assault on a Peshawar school that killed 151 people, mainly children, the Pakistani army says.

Another man - involved in the December 16, 2014, school attack - was sentenced to life in prison, according to an army statement on Thursday.

Among the seven sentenced to death was a man implicated in a deadly attack on soldiers in Karachi.

The army statement did not specify the date of the incident in the city's SafooraChowk neighbourhood.

The army said six of the convicts were members of the Tawhid-wal-Jihad group, while the other two were from Pakistan's Tehreek-e-Taliban and Jaish-e-Mohammad groups.

Army chief General Raheel Sharif confirmed the sentences, but it was unclear when they would be carried out.

Al Jazeera's Kamal Hyder, reporting from Islamabad, said the Pakistani people were in favour of the death penalty and wanted the military to conduct speedy trials.

"There is support on the ground. However civil rights organisations would not be supporting the move, saying the death penalty should be abolished," he said.

Tawhid-wal-Jihad was established in the late 1990s by Abu Musab al-Zarqawi, who went on to lead al-Qaeda's Iraq affiliate, a precursor of the Islamic State of Iraq and the Levant (ISIL) group, before he was killed in a US air strike in 2006.

Pakistan's military says the men belonging to Tawhid-wal-Jihad played a major role in planning and facilitating the school attack and several other assaults.

However, the school attack was claimed at the time by the Tehreek-e-Taliban.

Shock and outrage over Pakistan massacre

In the attack on the Army Public School in December, explosions and gunfire rang out as seven armed men rampaged through the school in one of the bloodiest events in Pakistan's history, killing 151 people, including 125 children.

Officials told Al Jazeera at the time that all seven attackers were killed in an operation shortly after the assault.

The event shocked Pakistanis and led the country to lift a moratorium on executions that had been in place since 2008.

Pakistan's parliament then amended the constitution to allow military courts to try civilians in terrorism cases.

The Supreme Court upheld the use of such trials earlier this month.

The army said the trials were fair and that the accused could appeal their convictions.

In February Pakistan announced the arrest of 12 members of the Pakistani Taliban over their alleged involvement in the school attack, and said another nine members of what was believed to be a 27-member cell had already been killed.