A powerful explosion struck a bus in downtown Kabul during rush hour on Monday, officials said, sending smoke rising in the sky just days after a deadly insurgent assault on Afghanistan's biggest military hospital.
At least one woman was killed and eight others wounded in the blast, which left the bus badly mangled and the area littered with charred debris and twisted metal.
No group has so far claimed responsibility for the assault, but it comes as the Taliban step up attacks even before the official start of the annual spring offensive.
"There has been an explosion against a minibus in Kabul," Kabul police spokesman Basir Mujahid told AFP, adding that more casualties were feared. "Police are investigating the nature of the explosion."
Gunmen disguised as doctors stormed Afghanistan's largest military hospital last Wednesday, killing more than 100 people in a brazen six-hour attack, multiple surviving staff and security sources told AFP.
Insiders including two interns already positioned inside the facility were among the attackers, the sources said.
The carnage inside the heavily guarded hospital points at a spectacular intelligence failure and spotlights how insurgents have managed to infiltrate top government and military institutions in Afghanistan.
The savagery of the assault was characterised by how the assailants stabbed bed-ridden patients, threw grenades into crowded wards and shot people from point-blank range.
The Islamic State group claimed it was behind the attack via its propaganda agency Amaq -- hours after the Taliban denied responsibility.
But the survivors AFP spoke to said the attackers chanted "Allahu Akbar" and "Long live Taliban" in Pashto.
The Taliban, Afghanistan's largest militant group, is known to distance itself from attacks on medical facilities or those that result in high civilian casualties.
The violence underscores rising insecurity. The country is bracing for an intense fighting season in the spring as the government's repeated bids to launch peace negotiations with the Taliban have failed.
Afghan forces, already beset by record casualties, desertions and non-existent "ghost soldiers" on the payroll, have been struggling to beat back insurgents since US-led Nato troops ended their combat mission in December 2014.
Kabul last month endorsed US General John Nicholson's call for thousands of additional coalition troops to hold off the militants before the spring offensive.
Extra troops were needed to end the stalemate in the war, Nicholson, the top US commander in Afghanistan, told the US Congress in what could be President Donald Trump's first major test of military strategy.
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