The attack, which came during morning rush hour on a busy road near the US embassy and NATO headquarters, killed mostly civilians, an interior ministry spokesman told AFP without giving a breakdown.
NATO said three coalition soldiers had received "non-life threatening wounds".
"(They) are in stable condition, and are currently being treated at coalition medical facilities," a spokesman for US Forces-Afghanistan said, without confirming their nationalities.
No group has yet claimed responsibility for the blast, which underscores the threat faced by international and Afghan forces against the resurgent Taliban as the US seeks to craft a new strategy in Afghanistan and NATO mulls boosting troop levels.
The blast, which NATO said was an improvised explosive device (IED), damaged two of the heavily armoured MRAP (Mine Resistant Ambush Protected) vehicles carrying the foreign soldiers and left a small crater in the road, witnesses and an AFP photographer said.
MRAPs, which are designed to withstand large explosions, are routinely used by international forces moving around Kabul.
At least three civilian cars were also damaged, with one ablaze, while windows even several hundred meters away were shattered. Firefighters and ambulances rushed stunned survivors to hospital.
One security source told AFP that a white Toyota Corolla had exploded as the convoy drove by, though that had not been verified by officials.
Pentagon chief Jim Mattis warned of "another tough year" for both foreign troops and local forces in Afghanistan when he visited Kabul last month.
He would not be drawn on calls by NATO commander in Afghanistan General John Nicholson for a "few thousand" more troops to break the "stalemate" against the insurgents.
But NATO chief Jens Stoltenberg told a German newspaper Sunday that the 28-nation alliance was considering boosting its troop strength once more given the "challenging" security situation.
The US has around 8,400 troops in the country with about another 5,000 from NATO allies. Most are taking part in NATO's train, assist and advise mission, though some are also carrying out counter-terror missions targeting the Islamic State group and Al-Qaeda.
- Grinding conflict -
The Afghan conflict is the longest in US history -- US-led NATO troops have been at war there since 2001, after the ousting of the Taliban regime for refusing to hand over Osama bin Laden following the 9/11 attacks in New York and Washington.
Afghan forces have been straining to beat back the Taliban insurgents since US-led NATO troops ended their combat mission in December 2014.
The annual so-called "spring offensive" announced last week normally marks an upsurge in fighting during warmer weather, though this winter the Taliban continued to battle government forces.
Already beset by killings, desertions, and struggles over leadership and morale, they faced "shockingly high" casualties in 2016 and the first part of 2017, according to a US watchdog SIGAR.
The report did not include a massacre at a base near northern Mazar-i-Sharif last month which saw militants dressed in army uniforms slaughter at least 144 Afghan recruits, according to a US official.
With more than one third of Afghanistan outside of government control, civilians also continue to bear a heavy brunt, with thousands killed and wounded each year and children paying an increasingly disproportionate price, according to UN figures.
Kabul province had the highest number of civilian casualties in the first quarter of the year due to attacks in the capital, a recent UN report showed. Most were carried out by the Taliban, though Islamic State claimed several which targeted Afghanistan's Shiite minority.
The UN had called on all groups to "take every measure possible to prevent unnecessary and unacceptable harm to Afghan civilians".