"Warm socks are so rare and they can easily be traded for cash in the North. One pair of socks fetches about 10 kilos of corn, which is enough to sustain a person for a month."
Socks and many other daily necessities are in short supply in North Korea, which pours money and resources into building up its 1.2-million-strong armed forces under its Songun, or military-first, policy.
Activists, many of them defectors from the North, regularly send leaflets over the border lambasting the regime and urging popular uprisings like those in the Middle East and North Africa in the past year.
The launches infuriate Pyongyang, which has threatened to open fire at launch sites.
Tensions have been high on the Korean peninsula since the conservative administration in Seoul rolled back the previous liberal government's "Sunshine Policy" of reconciliation and took a tougher stance toward Pyongyang.
Seoul also stopped its annual major food and fertiliser shipments to the North although it has been allowing humanitarian aid by civic groups, mostly modest in scale.
North Korea's leader Kim Jong-Il died on December 17 to be succeeded by his youngest son Jong-Un.
The North under its new leader has taken a hostile tone with the South's government, accusing it of failing to respect the mourning period for the late leader.
- AAP