Vietnamese enterprises have invested a combined US$2.65 billion into their overseas projects in the first three months of this year, the Foreign Investment Agency (FIA) has reported.

Newly-registered projects account for $720.7 million of the sum, while $1.9 billion goes to additional investments in five projects, according to the FIA, an agency under the Ministry of Planning and Investment.

The most remarkable additional investment in Q1 is that of the Vietnam National Oil and Gas Group, or PetroVietnam, which hiked its investment in a project operated by its joint venture Rusvietpetro in Russia to $1.4 billion.

It is followed by the Vietnam National Chemical Group, which added $518.9 million worth of investment into its salt project in Laos.

In the first quarter, local companies continued to invest mostly in the mining sector, which accounted for 72.3 percent of the total registered capital. It is followed by food and lodging services, with three new projects worth $335 million, and information and communication, with a total registered capital of $237.7 million.

In Q1/2013 alone, Vietnamese businesses have registered to invest in 12 nations and territories. Russia received the highest investment in the first quarter with $1.4 billion, or 52.7 percent, followed by Laos, 20.1 percent, and Myanmar, 11.3 percent.

As of March 20, Vietnam had 742 outbound projects in 59 countries and territories, with a combined registered capital of $15.5 billion.

Laos is the country that has so far attracted the most investment from Vietnamese investors -- more than $4.2 billion, or 27.1 percent of the total figure. There are currently 227 projects by Vietnamese enterprises in the Southeast Asian country, accounting for 30.6 percent of the total number.

It is followed by Cambodia, Russia and Venezuela.