The number of North Korea's mobile service subscribers stood at 450,000 late last year, only two years after the service began there, Vice Unification Minister Uhm Jong-sik said Tuesday.

Uhm was speaking at an economic forum hosted by Chosun Biz, the business website of the Chosun Media Group.

"The North can't remain a closed society forever," Uhm said. "We need to make preparations now to build a communication infrastructure for the era of reunification between the two Koreas." He added there is a need to study the unification process in Germany.

Prof. Song Tae-su of the Korea University of Technology and Education said, "After the Berlin Wall fell, the German government's top priority for the development of the former East Germany was to build infrastructure to boost the information and communication sector. That's why it launched a project to build infrastructure for a total of 60 billion Deutsche marks (approximately W32 trillion)."

Domestic and foreign communication and economic experts from the U.K., China and Germany and elsewhere as well as North Korean defectors took part in the forum.