KABUL: Two people were killed in a blast targeting workers for an Afghan television station Sunday, while elsewhere in the war-torn nation at least seven police officers died in an "insider attack" by Taliban loyalists, officials said.

The deadly attacks come amid surging violence across Afghanistan even while the US is negotiating with the Taliban for a possible peace agreement.

The first attack occurred in Kabul, when a "sticky bomb" -- a type of homemade device often attached to vehicles with magnets -- went off around 5:30 pm (1300 GMT), interior ministry spokesman Nasrat Rahimi said.

A "bus carrying the employees of Khurshid TV exploded in the Taimani area", he said, referring to a bustling neighbourhood in central Kabul.

"Two bypassers killed, and four others, including three employees of Khurshid TV injured."

Social media pictures showed a white minibus with extensive damage to its front. Zabiullah Doorandish, a journalist with Khurshid TV, said three of his colleagues had been injured, including one journalist.

"We had received a warning recently by the (security services), that the Taliban may target us," he told AFP.

No group immediately claimed responsibility but the Taliban in June threatened media outlets broadcasting anti-Taliban advertisements.

"They shall become military targets for the mujahideen in the capital, provinces, cities and rural areas and none of their offices, journalists, workers and personnel shall retain any immunity," the Taliban said in a June 24 statement.

Doorandish said he had not seen any anti-Taliban ads on the channel.

According to its Facebook page, the private Khurshid TV station is dedicated to showing cultural programmes that "preach the main values of journalism, democracy, national unity, creation of understanding & trust among people".

Afghanistan is the world's deadliest place for journalists, who face many risks covering the conflict and who have sometimes been targeted for doing their job.

On Twitter, Afghan President Ashraf Ghani called the bus attack "a war crime".

"I strongly condemn the attack on Khurshid Media. Deliberately targeting media and civilians is a war crime and those responsible will be held accountable," he wrote.

"Words cannot express how saddened I am to hear of your loss. I send my deepest condolences to the affected families."

- 'Infiltrators' -

In the southern province of Kandahar, at least seven Afghan police officers were killed when a group of colleagues thought to be loyal to the Taliban opened fire, officials said.

Jamal Naser Barekzai, spokesman for Kandahar's provincial police chief, said the attack occurred at a police checkpoint.

"There was an insider attack involving eight Taliban infiltrators at a police post in Shah Wali Kot district this afternoon, in which seven policemen were killed, one injured," Barekzai told AFP.

"The Taliban infiltrators have fled, and we have deployed additional forces to the area."

Another security official put the toll at 11, while the Taliban claimed their infiltrators had killed 14 "gunmen".

Insider attacks, sometimes referred to as "green on green," are a constant threat in Afghanistan for international and Afghan forces alike.

On July 29, an Afghan soldier killed two US troops as they were visiting an Afghan army base during in Kandahar.

That came two weeks after another Afghan soldier shot and killed an influential Afghan army colonel while he was conducting a security assessment in Ghazni province.

Civilian casualty rates across Afghanistan jumped back to record levels last month, following a dip earlier in the year, the UN said Saturday. —AFP