KABUL: An Afghan official says four people, including a district chief, have been killed by a roadside bomb in a region of northern Afghanistan that has been largely peaceful until now.

Senatullah Tumor, the spokesman for the governor of northern Takhar province, said Sunday that the bomb killed Hamidullah Haqjo Ashkamesh, chief of the Ishkashim district, as well as a police officer and two of his bodyguards.

The Taliban claimed responsibility for the attack. The Taliban's 14-year insurgency has spread in recent months from its strongholds in the south to northern Afghanistan.

Taliban 'shadow governor' killed in air strike

Afghanistan's internal intelligence agency said that the Taliban's senior commander ─ known as a shadow governor ─ for the eastern province of Kunar was killed on Sunday along with two other commanders in an air strike.

The United States-led coalition force did not immediately confirm it carried out the raid.

Missile strikes by unmanned drones and other aircraft are one of the remaining actions of US and allied forces who remain in Afghanistan after the official end of combat operations at the end of last year.

The Afghan Taliban's annual “spring offensive” began in April 2015, with the militant outfit vowing nationwide attacks in what is expected to be the bloodiest fighting season in a decade as Nato forces pull back from the frontlines.

This year’s offensive marks the first fighting season in which Afghan forces will battle the insurgents without the full support of US-led foreign combat troops.

“The Islamic Emirate is going to launch the spring operations under the inspirational name of ‘Azm’ (Determination) at 5 am on 24th April 2015,” the Taliban said in a statement in April.

“The main targets of these operations... will be the foreign occupiers, especially their permanent military bases... officials of the stooge regime, their military constellations, especially their intelligence, interior ministry and defence ministry officials.”

Meanwhile in southern Kandahar province, police say a roadside bomb killed a woman and wounded three people in the province's Khakrez district.

Read more: Taliban claim killing 17 police in southern Afghanistan