Robberies are on the rise in Hoi An Town in Quang Nam Province, apparently perpetrated by drug addicts targeting local and foreign tourists, police say.

Hoi An police say reports of robberies have been rising since 2012, with 20 theft cases that year, rising to 30 cases of robbery in 2013 and 37 cases in 2014, with 21 arrests made this year alone. 31 out of the 37 robberies in 2014 were targeted at foreign tourists, while the rest six at local women and children.

Most vulnerable were visitors on bicycles and on foot in empty Hoi An streets, they said.

Visitors were robbed of valuables and documents, such as passports, Not only the visitors had lost valuable items, they were also robbed of identification documents such as passports On December 6, a Vietnamese teacher had her bag snatched while riding on a motorbike. She fell from the motorbike during the theft and suffered severe head trauma.

Colonel Tran Dung, the deputy head of Hoi An Police, said the robbers are believed to be selling identification documents and advised foreign tourists to contact police and their embassies immediately to have them cancelled and get new papers.

Lieutenant Colonel Mai Ba, from Hoi An Police, said he did not have enough officers but had put "50 to 70 officers on street patrol, though robberies are continuing to escalate."

Police say most of those arrested were drug addicts from other provinces and fear robberies will rise with the approach of Tet as more visitors come to Hoi An during the holiday period.