Updated Oct 4. Still valid Oct 5
From UK: Foreign and Commonwealth Office
Most visits to Vietnam are trouble free but you should remain alert and be on your guard. Petty crime is not confined to the backpacker districts but also occurs in the main tourist shopping areas. Do not walk in secluded locations alone, or with people you do not know. There is low reporting of sexual assaults but tourists should travel with friends and take the normal precautions.
Violent attacks against tourists have been reported in urban areas, as well as popular tourist areas, including Cat Ba and Nha Trang in the early morning or late at night. Some reports involve tourists being attacked while on a xe om (motorcycle taxi) or during disputes about being overcharged.
Use larger metered taxis to minimise the risk of robbery or overcharging. Be on your guard against pickpockets and avoid carrying handbags or wearing expensive looking jewellery or watches. Use hotel safety deposit boxes to store valuables, money or passports and carry a photocopy of the data page of your passport.
There have been reports of scams targeting tourists, involving fake charities, gambling and taxis.
There have also been reports of arguments over hotel, restaurant or taxi bills turning violent or abusive.