A wave of bombings has crippled the tourism industry in Kenya, known as one of the world's top tourist destinations, famous for its wildlife safaris and pristine white beaches on the Indian Ocean.

Many visitors have stayed away because of terrorist attacks in Nairobi and the coast, while some tour companies have evacuated their clients.

"Tourism, especially in the coastal region, is at an all-time low," Lucy Karume, head of the Kenya Tourism Federation, says.

"We are 70 to 80% down on the coast."

Tourism accounts for more than 12% of the East African country's gross domestic product, generating up to 100 billion shillings (AU$1.19 billion) annually, says Mike Macharia, chief executive of the Kenya Association of Hotels and Caterers.

Macharia says tourism gives direct employment to half a million Kenyans and supports ten times that number, if family members and indirect employment are taken into account.

Tourism plunged by 15% in 2013 because of fears of insecurity surrounding national elections and following an attack by the Somali Islamist group al-Shabaab on Nairobi's Westgate shopping mall that claimed at least 67 lives.

In recent months, attacks in Nairobi and in the Mombasa region on the coast have been blamed on al-Shabaab. Dozens of people – none of them tourists – have been killed.

Most of the Nairobi attacks have targeted buses, markets, restaurants and a police station in or near Eastleigh, a neighbourhood with a large Somali population.

In May, attacks on the coast included an explosion outside a large tourist resort north of Mombasa and a bombing at a bus station in the city.

Macharia estimates that Kenya lost about $US10 million (AU$10.82 million) in cancellations in May. "What is worst is not the cancellations, it is the lack of new bookings."

Some hotels are placing staff on leave, and casual labourers have already been let go. The manager of one upscale Maasai Mara game lodge told dpa she is looking for a new job in neighbouring Tanzania, which competes with Kenya in offering safaris and beach holidays.

Australia has advised its citizens to exercise a high degree of caution in Kenya and to reconsider travelling to Nairobi and Mombasa.

The Department of Foreign Affairs and Trade also advised against travelling to border regions with Somalia, South Sudan and Ethiopia.

Yet Sarah Anderson, the local representative of the Kenyan Tourist Board, claimed the downturn in travel to the coastal areas has not hit arrivals from Australia.

"Kenya's coastal areas with its beach resorts have lured UK and US travellers in the past but Australians are drawn by the once-in-a-lifetime safari experience," she said.

"For those is us that know and love Kenya it is so saddening to see some areas hit by terror attacks, but these are not happening in the National Parks where Australian tourists spend their time and we have many Australians travelling in Kenya right now having wonderful experiences."

Anderson added that some Australians heading to Kenya for the annual wildebeest migration next month are limiting their time in Nairobi and staying longer on safari. 

Africa specialist Swagman Tours claimed its Kenya bookings have slipped only 2% in recent months.

While most travellers have moved their Nairobi accommodation away from the city centre, or transiting without staying in the capital "most are continuing with their plans", director Wayne Hamilton said.

Insurance concerns prompted two major British tour companies to cut short the holidays of hundreds of clients and to evacuate them under armed guard.

The United States has sent marines to guard its embassy in Nairobi, where officials say staff will be reduced. Germany has cautioned against visiting the north-east near Somalia.

Kenya's government and tourism industry have lashed out at Western governments for their travel advisories.

They claim the warnings are politically motivated and a form of economic sabotage, and argue that similar warnings have not been issued for other countries undergoing comparable unrest.

The West has had frosty relations with Kenya since the election in March 2013 of President Uhuru Kenyatta, who faces charges at the International Criminal Court of murder, rape and forced displacement.

Kenya's police response to years of escalating terrorism has been lackluster. The main initiatives this year are a neighbourhood watch program, a ban on tinted windows in cars, and a controversial mass roundup of Somali immigrants.

"There is no threat to any foreigner or any Kenyan in Mombasa," the city's police chief, Robert Kitur, says.

He says there are more uniformed and undercover officers on the coast, including armed beach patrols and escorts for tourists travelling from the airport to resorts.

Hotels are screening guests. Many have hired extra security and installed surveillance cameras.

Despite all the concern, tourists who have come to Kenya often love it. "Kenya exceeded our expectations," says Patricia Stevens-Kopf from Nebraska in the United States.

"It is all just breathtaking," she said on the last day of her multi-week safari with her husband. "The elephants were mesmerising."

Stevens-Kopf said she felt secure and impressed by the number of police officers and hotel security guards.

Kenyan authorities and tourism industry have launched online campaigns to reassure tourists.

Hotels are slashing prices, and some coastal resorts are even giving away free nights for visitors with longer stays.