Taliban militants attacked foreign tourists escorted by an Afghan army convoy in western Herat province on Thursday, leaving at least six people wounded as the insurgents step up nationwide attacks.

The nationality of the tourists, travelling from neighbouring provinces of Bamiyan and Ghor, was not immediately known and the Taliban have officially not claimed responsibility for the attack so far.

‘The convoy was ambushed by the Taliban in Chesht-e-Sharif district in Herat,’ said Jilani Farhad, the spokesman for Herat's governor.

Military spokesman Najibullah Najibi said the ambush left at least five foreign tourists and their Afghan driver wounded, adding that the insurgents had been repelled and the foreigners were being escorted to Herat city.

The attack comes as Taliban militants intensify their annual summer offensive after a brief lull during the holy fasting month of Ramadan, which ended in early July.

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

The latest attack follows a Taliban truck bombing on Monday at a hotel for foreigners in Kabul, which triggered a seven-hour gun and grenade assault that highlighted growing insecurity in the city.

The guests and staff of the Northgate hotel escaped unharmed, but one policeman was killed after the suicide truck bomber paved the way for two other armed insurgents to enter the heavily guarded facility near Kabul airport.

The attack was a grim reminder of growing insecurity in Afghanistan since most foreign troops withdrew in 2014. The rising violence has resulted in large civilian casualties.

Foreigners are also increasingly being targeted as the conflict escalates.

The United States has warned its citizens in Afghanistan of a ‘very high’ kidnapping risk after an American citizen narrowly escaped abduction in the heart of Kabul.

American journalist David Gilkey and his Afghan translator were killed in June while travelling with an Afghan army unit that came under fire in southern Helmand province.

Aid workers in particular have increasingly been casualties of a surge in militant violence in recent years.

Judith D'Souza, a 40-year-old Indian charity worker, was rescued in late July, more than a month after she was taken at gunpoint near her residence in the heart of Kabul.

D'Souza's abduction came after Katherine Jane Wilson, a well-known Australian NGO worker, was kidnapped on April 28 in the city of Jalalabad, close to the border with Pakistan.

In 2007, the Taliban seized 23 South Korean aid workers from a church group travelling through southern Afghanistan. The militants killed two men before releasing the rest, reportedly in return for ransom payments.