Foreign tourists falling prey to unscrupulous street vendors in Vietnam, especially in Ho Chi Minh City, is an old story.

Coconut-water vendors have recently joined the list and have become ubiquitous on the streets of District 1, ready with their traps to ensnare the innocent.

A man in his 40s, hailing from the Mekong Delta city of My Tho, sells a coconut worth VND15,000 at most for $5-10 in front of Taka Plaza shopping center on Nam Ky Khoi Nghia Street.

This is his modus operandi: as soon as a group of tourists stop before his cart and before they tell him how many or even that they want to buy he picks up a machete and at lightning speed slices one coconut each for all of them.

The tourists are forced to pull out their wallets and pay the ridiculous price he demands. After all, who wants to argue or quarrel with a man with a machete?

He also demands $10-20 if a tourist wants to take photographs of his coconuts.

N., a security guard at Taka Plaza, says he repeatedly warns tourists but many still fall into the trap.

He says a vendor on the other side of the road is equally bad.

"There were these tourists who had to pay VND1 million ($47) for nine coconuts, and then the greedy vendor demanded an additional VND800,000," he says about a transaction.

The two sides argued but finally the tourists had to pay, he says.

Outside the War Remnants Museum on Vo Van Tan Street, District 3, a group of vendors always hang around to offer tourists illegal copies of books.

Since the books do not carry the price, the vendors usually rip off tourists, who often end up paying $30-50 for a book worth VND100,000.

Woe betide any tourist flicking through a book and then trying to return it: the vendor will yell, other vendors are likely to heap scorn, causing the hapless visitor to buy the book to avoid any possible unpleasantness.

Many tour guides told Vietweek about a particularly nasty bookseller who usually stands beside the museum gate and threatens any guide who tries to prevent tourists from buying.

In the first half of this year the number of foreign arrivals in Vietnam was up just 2.6 percent year-on-year. It had increased 13.9 and 18.1 percent in 2011 and 2012, respectively.

On September 4 Prime Minister Nguyen Tan Dung issued an instruction aimed at improving tourism management and ensuring visitors' safety.

It requires authorities in cities and provinces to install cameras at places known to be frequented by pickpockets, street vendors, and beggars.