BERLIN (REUTERS) - Germany's foreign ministry said on Friday (Aug 12) further attacks may hit Thailand after a series of blasts at three of the country's resorts and advised visitors to show "extreme caution".

Thailand is a popular holiday destination for Germans.

Two people were killed and dozens wounded in the blasts, which targeted three of the most popular resorts late on Thursday and on Friday, days after Thais voted in a referendum to accept a military-backed constitution.

"Further attacks cannot be ruled out. Therefore the foreign ministry advises extreme caution. People travelling to Thailand are recommended to avoid public places and crowds of people, to follow the media closely," the ministry said in its travel advice.

The ministry also confirmed that three Germans had been injured in the attacks.

Tourism accounts for about 10 per cent of Thai national output and has been one of the few bright spots in a sluggish economy.