It was the latest in a series of suicide attacks in the Afghan capital that coincide with renewed efforts to revive a peace process with Taliban insurgents that broke down in July, Reuters wrote.
The bomber targeted a vehicle owned by a company that works with Tolo News, Afghanistan's first 24-hour news channel, Kabul Police Chief Abdul Rahman Rahimi told reporters. He did not say how many of those in the van were killed or wounded.
The Taliban openly threatened to target the television channel last year after it reported allegations of summary executions, rape, kidnappings and other abuses by its fighters during the battle for Kunduz. The Islamist insurgents briefly captured the northern city last year, their biggest success in the 15-year insurgency, before being ousted by government forces.
There was no immediate claim of responsibility for Wednesday's attack. The Taliban, who are fighting to topple the Western-backed government in Kabul and reimpose strict Islamic law, could not be reached for comment. Tolo News has been one of the most active media operations in the country for years, employing dozens of journalists, many in volatile provinces.
Later reports said that the explosion occured near Russia's embassy. No Russian staff were hurt in the accident, the Russian Foreign Ministry said in a statement.
The latest attack adds a dangerous new complication for local journalists working in a country already ranked as low as 122 out of 180 in the World Press Freedom Index, a gauge of media freedom compiled by the group Reporters Without Borders.
At least 20 people were wounded in the bombing, including women and children, Ministry of Public Health spokesman Ismail Kawusi said.
Since the start of the new year, Kabul has seen at least six bomb attacks. On Sunday, a rocket landed near the Italian embassy in Kabul, wounding two security guards. Envoys from Afghanistan, Pakistan, China and the United States met in Kabul this week to explore ways to find a negotiated end to 15 years of war, and urged the Taliban to join peace talks. Separately on Wednesday, the U.S. government issued a warning that it had received reports militants were planning to attack a hotel or guesthouse frequented by foreigners in Kabul.