Cubans are bracing themselves for a clampdown on the flow of car tyres, flatscreen televisions, blue jeans and shampoo in the bags of travellers who haul large amounts of foreign-bought merchandise to an island where consumer goods are frequently shoddy, scarce and expensive.

Hundreds of thousands of Cubans and Cuban-Americans fly to and from the island each year thanks to the easing of travel restrictions by the US and Cuban governments over the past five years.

Their Cuba-bound checked baggage has become a continuous airlift that moves nearly $2bn (£1.2bn) of products ranging from razor blades to rice cookers. The baggage carousels at Cuba's airports often look like they're disgorging the contents of an entire Wal-Mart or Target store. Many families bring special trailers to carry the bags of their returning family, which often weigh many hundreds of pounds and include items such as bicycles and flatscreen TVs.

But the Cuban government on Monday is enacting new rules sharply limiting the amount of goods people can bring into the country in their luggage, and ship by boat from abroad.

The government says the restrictions are meant to curb abuses that have turned air travel in particular into a way for professional "mules" to illegally import supplies for both black-market businesses and legal private enterprises that are supposed to buy supplies from the state.

Among ordinary Cubans, reactions have ranged from worry to outrage that their primary, and for many only, source of high-quality consumer goods may be throttled.

"People are really unhappy," said Maite Delgado, a 75-year-old retired state worker. "All the clothes and shoes that I have come from my granddaughters in Spain or my siblings in the US."

The rules that come into effect Monday run to 41 pages and give a sense of the quantity and diversity of the commercial goods arriving in checked bags. Travellers will be allowed to bring in 10 kg of detergent instead of 44; one set of hand tools instead of two; and 24 bras instead of 48. Four car tyres are still permitted, as are two pieces of baby furniture and two flatscreen televisions. Cuban customs also bars passengers from bringing in items worth more than $1,000. Rather than examining receipts, customs agents are given a long list assigning pre-set values to certain goods ($250 for a video-game console, for example.) Those prices rise sharply under the new rules, making it far easier to reach that $1,000 limit.

The new rules similarly increase the duties paid on goods shipped from abroad, another major source of foreign merchandise for the island.

Authorities have taken to the airwaves and state media in recent days to assure Cubans that the vast majority of travellers won't be affected. The change is intended "to keep certain people from using current rules on non-commercial imports to bring into the country high volumes of goods that are destined for commercial sale and profit," Idalmis Rosales Milanés, deputy chief of Cuban customs, told government newspaper Granma.

The government has justified the new rules with examples of prolific "mules", including one passenger it said brought in 41 computer monitors and 66 flatscreen TVs in a year.

Between $1.7bn and $1.9bn-worth of goods were flown to Cuba in travellers' baggage last year, with the average flyer bringing in goods worth $3,551, according to a survey by the Havana Consulting Group.

"It's sustenance, support that greatly aids in the survival of the Cuban family," the consulting group president, Emilio Morales, said. "Along with cash remittances, it's the most significant source of earnings for the Cuban population, not the salaries the government pays."

While his study did not look at the final destination of travellers' goods, Morales said he estimated based on his knowledge of the phenomenon that about 60% went to families and 40% to black-market retailers.

With foreign reserves dropping sharply over the past two years as Cuba tries to pay off sovereign debt and make itself a more attractive destination for foreign investment, Morales said, the government is desperate to reduce the flow of goods and push Cubans' relatives abroad to send help in the form of cash remittances, which are subjected to hefty government fees. Limiting informal imports also would presumably help boost business in state-controlled stores.

The rule change has already had an effect in Miami, where many stores are dedicated to selling goods to island-bound Cubans and Cuban-Americans.

"I haven't sold almost anything this morning," said Diana Calzadilla, 28, a cashier at Cadalzo Fashion, a store in Miami's Little Havana neighbourhood that sells discount clothing and accessories to travellers on their way to Cuba. "People look around but they don't buy anything because they're not sure how much they're going to be able to bring."

Several "mules" have commented that they are going to look into other ways to make money, she said. At least one customer, she said, appeared decided.

"It was their last trip," she said. "They don't know if they'll go again."