The vouchers offer $100 towards accommodation in the centre of Adelaide and $50 for accommodation in the city's suburbs or in regional centres.

They go online from Tuesday, with successful applicants having until the end of March to travel, and will cost the government more than $2 million.

The majority will be available to South Australians with some available to people from other states.

"The first round of vouchers injected $10 million into our state's economy, with the tens of thousands of discounted room night bookings giving people more time and more money to spend on experiences," Premier Steven Marshall said.

"With an additional round expanded to include interstate travellers, who we know spend more than intrastate, as well as the peak summer holiday period this stimulus comes at exactly the right time to further bolster tourism businesses and create jobs."

But Opposition Leader Peter Malinauskas said the government had failed in not extending the vouchers to cover hospitality venues, tours and attractions.

"Our tourism and hospitality sector has been hit hard by the pandemic and the government is failing, once again, to provide broad support to this critical industry," Mr Malinauskas said.

Mr Marshall said those issues would be addressed in a likely third round of vouchers.

Australian Associated Press