At least 25 other people were wounded in the bombing near the Russian embassy in downtown Kabul, marking the first major attack on an Afghan media organisation since the Taliban were ousted from power in 2001.
No group has so far claimed responsibility for the carnage, as violence escalates despite an international push to jumpstart Taliban peace talks.
"In the terrorist attack today in... Kabul, we lost seven staff members," TOLO, a privately run news and entertainment station that is often critical of the Taliban, said on Twitter.
The loud explosion sent a plume of smoke rising in the sky, with ambulances and firefighters rushing to the scene which was littered with charred debris.
"The enemy of humanity, peace and Islam martyred our colleagues because they were exposing their crimes," TOLO news presenter Fawad Aman said in a live broadcast.
"They martyred you to silence us, but they will never achieve this evil goal."
The Taliban in October declared TOLO and 1TV, another privately run news channel, as legitimate "military targets".
The group said the move was in response to their reports claiming that Taliban fighters raped women at a female hostel in Kunduz, after the group briefly captured the northern city in late September last year.
The Taliban rejected the reports as fabrications, saying they were examples of propaganda by the "satanic networks".
"No employee, anchor, office, news team and reporter of these TV channels holds any immunity," the Taliban said at the time.
Delegates from Afghanistan, Pakistan, China and the United States convened in the Afghan capital Monday for a one-day meeting seeking a negotiated end to the 14-year Taliban insurgency.
