A group of anti-nuclear activists from across Asia gathered in central Seoul to voice their opposition to the upcoming Nuclear Security Summit, the largest international event South Korea has ever hosted.About 30 anti-nuclear activists from countries such as Japan, Thailand and China’s Taiwan held a news conference on Monday to call for a nuclear free world. The activists, in solidarity with South Korean civil activists, carried placards condemning the nuclear security summit that will take place on March 26-27 in Seoul and plans to build more nuclear power plants.  The protesters also held banners reading "No more Fukushima” and "A nuclear free world for children.”The upcoming Nuclear Security Summit in Seoul is expected to draw about 50 world leaders, including U.S. President Barack Obama and Chinese President Hu Jintao. Obama hosted the first summit in 2010, saying that the world should work together to bolster international safeguards and prevent nuclear terrorism.