Herat (Afghanistan) (AFP) - Taliban militants attacked a group of 12 American and European tourists escorted by an Afghan army convoy in western Herat province Thursday, leaving at least seven people wounded as the insurgents step up nationwide attacks.

The tourists -- eight British, three Americans and one German national -- were ambushed by Taliban gunmen in the restive district of Chesht-e-Sharif, while en route from the neighbouring provinces of Bamiyan and Ghor.

It is unclear why they were travelling overland at a time when Western embassies typically warn their citizens against all travel in Afghanistan, citing threats of kidnapping and attacks.

"The foreign tourists -- three Americans, six Britons, two Scots and one German -- were travelling with an Afghan army convoy when they were ambushed by the Taliban in Chesht-e-Sharif," said Jilani Farhad, the spokesman for Herat's governor.

He said the insurgents had been repelled and the foreigners were being escorted to Herat city, adding that the attack left at least six foreigners and their Afghan driver wounded.

Local authorities released photographs of some of the foreigners being treated in a district hospital for apparently minor injuries.

The Taliban claimed the attack on "foreign invaders" as they 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.

But that has not stopped some foreign tourists from travelling to Afghanistan, endowed with stunning landscapes and archaeological sites, many of them in volatile areas prone to the Taliban insurgency.

The Guardian newspaper reported the tourists came to Afghanistan with Hinterland Travel, an England-based adventure travel company which offers tours passing through central and north Afghanistan as well as volatile lapis mines in the country.

The company was not immediately reachable for comment. Its latest 21-day tour through "glorious, stark mountain passes" in Bamiyan and Herat started on July 26, according to its website.

- Warzone tourism -

James Willcox, founder of another England-based adventure travel operator Untamed Borders, said his agency stopped using the Bamiyan-Herat road in 2009 because "it's just not safe".

Bamiyan, famous for empty hillside niches that once sheltered giant Buddha statues that were blown up by the Taliban, is at the centre of Afghan efforts to boost revenue from warzone tourism.

A vast, ancient landscape of russet-hued cliffs, Bamiyan is a rare oasis of tranquility but it is wedged between insurgency-hit districts.

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.

Thursday's 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 the deteriorating security situation in Afghanistan since most foreign troops withdrew in 2014. The rising violence has resulted in large Afghan civilian casualties.

Foreigners are also increasingly being targeted as the conflict escalates.

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.