At least nine people have been killed across Afghanistan, including two children who were killed in an explosion while gathering firewood in the Zhari district of the southern Kandahar province, officials have said.

A separate bomb blast in the Shahwali Kot district of Kandahar wounded another 10 children, leaving seven in critical condition, said Samim Khopalwaq, the spokesman for Kandahar's governor.

"Our children were there to collect wood to burn when they were hit by this bomb," said Bismallah Jan, the father of one of the wounded children in the Shahwali Kot.

"The government should have cleared the area, it [is] their duty to protect us."

Afghanistan is one of the most heavily mined countries in the world, and children are often killed or wounded while playing, collecting firewood or tending animals.

In eastern Nangahar province bordering Pakistan, a bomb blast killed Judge Mohammad-ul Hassan and wounded two of his daughters in the provincial capital Jalalabad, police spokesman Hazrat Hussain Mashreqiwal said.

The judge served in neighbouring Laghman province.

Police academy attacked 

In another attack, fighters killed six people working on a road project, including the head of a construction company, in northern Baghlan province, police spokesman Jawed Basharat said, adding that the attack wounded another person and left two missing.

In eastern Khost province, three men launched a coordinated attack on a police academy using suicide bombers and gunmen.

Al Jazeera's Jennifer Glasse, reporting from Kabul, said one of the attackers detonated his explosives at the gates of the academy, while two others engaged in battles with security forces before detonating their devices.

The Taliban claimed responsibility for the attacks in Nangarhar and Khost. 

Taliban fighters have stepped up attacks on Afghan soldiers and police in recent months.

US and NATO forces concluded their combat mission at the end of last year and Afghan troops took charge from January 1.

Source: Al Jazeera and agencies