* Crowds smaller at square in the heart of Marrakesh
* Harder to encourage tourists to come and to return
By Zakia Abdennebi
MARRAKESH, Morocco, April 29 (Reuters) - Some tourists snapped the wreckage on their mobile phones. Some just wept.
The crowds in the Jamaa el-Fna, at the heart of Morocco's main tourist city, had dwindled on Friday, a day after a bomb killed 15 people at a Marrakesh cafe, most of them foreigners taking in the square's ever-moving spectacle.
"We arrived last night and decided to stay even after hearing the news, thinking that lightning cannot strike the same place twice," said David Collet, a Frenchman, stopping with a friend at an orange juice stall.
"It is also the best thing to do, to stand up to terrorism," he said.
Morocco has described the bombing as a terrorist attack, its deadliest in eight years. It has not said who was responsible for the explosion, likely to inflict damage on a tourist industry on which millions depend in the North African country.
The bomb ripped through the cafe at lunch time on the Jamaa el-Fna, where tourists take in the snake charmers, fortune-tellers and acrobats in a city established nearly a thousand years ago.
"We don't understand. Marrakesh is such a nice place," said German tourist Julia Zasho, who sobbed with her mother at what remained of the venue they used to visit frequently.
"What happened is a catastrophe for tourists."
It is also a catastrophe for a country that has no oil or gas and relies on tourism as the second-biggest employer after agriculture, a $7 billion a year industry accounting for nearly a 10th of gross domestic product.
Marrakesh, seen as a high-end destination with its markets, minarets and mountain backdrop, is the country's most lucrative spot.
A constant headache for Moroccan tourism officials has been to ensure more first-time visitors return to a country that has usually been a haven of stability in a volatile region.
At Marrakesh airport, French couple Jean-Pierre and Marie Arnault said they came every year.
"Next year we will go somewhere else," said Jean-Pierre.
Marie said: "Attacks happen all over the world, but this one targeted tourists."
French sports teacher Carole Cahuzac believed she had a narrow escape from the attack, having planned to go to Jamaa el-Fna on Thursday afternoon.
"I am not sure I will come back to Marrakesh," she said. (Writing by Souhail Karam; Editing by Matthew Tostevin)