KABUL: More than 20 people were killed in separate bomb attacks in Afghanistan on Monday, including at least 14 when a suicide bomber struck a minibus carrying Nepalese security contractors in the Afghan capital, officials said.

In Kabul, a Reuters witness saw several apparently dead victims and at least two wounded being carried out of the twisted remains of a yellow bus after the suicide bomber struck the vehicle during the morning rush hour in the capital.

Hours later, a bomb planted in a motorbike killed at least eight civilians and wounded another 18 in a crowded market in the northern province of Badakhshan, said provincial government spokesman Naveed Frotan. The casualty count could rise, he said.

The attacks are the latest in a recent surge of violence that highlights the challenges faced by the Afghan government in Kabul and its Western backers as Washington slowly draws down its remaining troops despite a persistent insurgency.

Interior Ministry spokesman Sediq Sediqqi said on Twitter that 14 people had been killed and eight wounded in the attack in Kabul. Police were working to identify the victims, he said.

"The suicide bomber targeted a minibus of security guards of a foreign company, right now we are working to identify the nationalities of the victims," said Sediqqi.

The casualties appeared to include Afghan civilians and Nepalese security contractors, Kabul police chief Abdul Rahman Rahimi said after police and emergency vehicles surrounded the scene in the Banae district in the east of the city.

He said the suicide bomber had waited near a compound housing the security contractors and struck as the vehicle moved through early morning traffic. As well as the bus passengers, several people in an adjacent market were also wounded in the attack, which occurred during Ramazan.

The Taliban claimed responsibility for the Kabul attack in a statement from the militant group's main spokesman, Zabihullah Mujahid, on Twitter. There was no immediate indication of who carried out the attack in Badakshan.

The Nepalese government was still working through its embassy in Pakistan, which also oversees Afghanistan, to verify reports that its citizens were involved in the attack, Foreign Ministry spokesman Bharat Paudel said.

Indian Prime Minister Narendra Modi sent his condolences to his two South Asian neighbours after the attack.

“We strongly condemn the horrible tragedy in Kabul. Our deep condolences to people & Govts of Afghanistan & Nepal on loss of innocent lives,” Modi said on Twitter.

Another explosion in Kabul later on Monday morning wounded a provincial council member and at least three of his bodyguards, Kabul police spokesman Basir Mujahid said. It was thought a bomb had been attached to the lawmaker's car, he said.

The attacks underlined how serious the security threat facing Afghanistan remains since former Taliban leader Mullah Akhtar Mansour was killed in a US drone strike last month and was replaced by Mullah Haibatullah Akhundzada.

The blasts follow a deadly suicide attack on a bus carrying justice ministry staff near Kabul last month and a separate attack on a court in the central city of Ghazni on June 1.

The Taliban claimed both those attacks in revenge for the execution of six Taliban prisoners.