HANOI, April 9 (Xinhua) -- Mobile phone service providers in Vietnam in the last few days have notified their customers that they should submit their portrait photos before April 24, otherwise they will be no longer able to make or receive calls, or send or receive messages.

According to Vietnam's new regulation mainly designated to prevent spams, new postpaid and prepaid mobile phone subscribers are supposed to provide their personal information and a portrait photo of themselves, while existing ones to add the photo, according to the Vietnam Telecommunications Authority on Monday.

Failing to provide portrait photos and accurate personal information, subscribers' contracts will be terminated, and the service providers will be fined.

Millions of spam messages are sent a day, mostly from prepaid mobile phone subscriptions which are not registered, or registered with false personal information, so the new regulation is aimed at reverse the situation, as well as to prevent swindling and other unwanted activities, said local officials.

However, many local residents argued that provision of portrait photos is unnecessary because when signing up mobile phone services, they have already been required to submit a copy of their identity card or passport which has their portrait photo.

Vietnam made total telecommunications revenues of 96.4 trillion Vietnamese dong (over 4.2 billion U.S. dollars) in the first quarter of this year, according to the country's General Statistics Office.