Reports say a Maldivian radical group affiliated with Islamic State says it carried out the attack in a video posted online.
Three men with suspected links to Islamic State have been arrested over the stabbing of two Chinese nationals and an Australian in the Maldives.
The attack happened on Tuesday night in Hulhumale, an island four miles (7km) north of the capital Male.
One of the Chinese nationals was a tourist and the two other victims worked in the city.
A Maldivian radical group affiliated with Islamic State said it carried out the attack in a video posted online, according to local news reports.
One of the three masked men seen in the video accused the Maldivian government of being run by infidels and warned more attacks would follow.
Last year, a 35-year-old man identified as a leader for Islamic State in the Maldives by US authorities was arrested for allegedly leading IS recruitment in the mainly Sunni Muslim nation.
Islamic State said it carried out deadly bombings in Sri Lanka in April last year, and has been looking to bolster its presence in the sub-continent after being driven out of its self-styled caliphate in Iraq and Syria.
The Maldives parliament has given sweeping investigative powers to counter-terrorism agencies, and authorities have stepped up operations against hardline Islamist groups.
Open source media and advice from the Foreign & Commonwealth Office highlight recent news concerning terrorism in the Maldives, a popular resort with the affluent and honeymooners. The most common problems are normally stolen passports together with swimming & diving accidents.