DENPASAR, Indonesia (REUTERS) - Indonesia's President Joko Widodo ordered more police at hotels, airports, shopping malls and across Bali after Thursday's attacks in Jakarta by Islamic State in Iraq and Syria (ISIS) militants.

Government officials fear the Jakarta attack, in which seven died including all five militants, could revive memories of Bali bombings in 2002 and 2005 and hinder the President's efforts to nearly double tourist arrivals to 20 million people by 2019.

Bali's economy is already growing at its slowest pace since the financial crisis.

"I'm a little scared but honestly there is probably more police out there right now," US tourist Mike Rosenthal told Reuters on one of Bali's famously beautiful beaches.

"I'm probably safer now - just got to be careful, stay low and avoid tourist areas."

Travel and tourism directly contributed around US$23 billion (S$33 billion) to Indonesia's economy in 2014, or about 3.2 per cent of gross domestic product, according to a report from the World Travel & Tourism Council.

At Bali's airport, tour guides said they were confident that any drop in business would be temporary.

"There is no problem. Bali is safe," said Yan Xiang Zhao, a tourist who had flown in from Taiwan with two friends.