Taliban on Tuesday kidnapped around two dozen people after pulling them off buses in southern Afghanistan, officials said, the latest in series of abductions on the country's increasingly dangerous highways.

The pre-dawn incident in Washer district of Helmand province comes a day after militants killed more than 20 people, including 14 Nepali security guards, in a wave of violence across the country.

"They abducted around 25 people, all men," the Helmand governor's spokesman Omar Zwak said. He was unable to give a more precise figure, but added the passengers were travelling on a bus and two trucks from southern Kandahar to western Herat province.

"Our latest report shows they have been taken to Marja district of Helmand. We have started our search and rescue operation," he said.

Marja district is the Taliban hotbed and a battleground between the Taliban and Afghan forces in volatile Helmand province.

Witness Agha Jan told AFP the militants, who were wearing army uniforms, initially detained 37 people.

"They released women and children later, but kept the men," he said.

The Taliban insurgents said they were targeting Afghan government officials aboard the vehicles.

"They have been taken based on the intelligence. Those who are innocent will be released and those who are working with the puppet Kabul administration will be brought to justice in Islamic Emirate's court," a spokesman for the insurgents said on Twitter.

Highways around Afghanistan passing through insurgency-prone areas have become exceedingly dangerous, with the Taliban and other armed groups frequently kidnapping or killing travellers.

Earlier this month, gunmen abducted 40 people in northern Kunduz province, releasing some later, but an unknown number of others remain in Taliban captivity.