The South Korean government allowed a Christian group to light a massive steel Christmas tree near the border last year for the first time in seven years as tensions flared in the wake of two deadly attacks blamed on the North.

That tree will be lit again this month, while South Korea has also decided to allow other Christian groups to light two other front-line Christmas trees, a Defense Ministry official said.

The decision is meant to help guarantee freedom of expression and religion, the official said on condition of anonymity, citing office policy.

Earlier on Sunday, North Korea’s state-run Uriminzokkiri website said that lighting the first tree was a form of psychological warfare and would trigger an "unexpected consequence."

South Korea’s military will bolster security near the three trees, located on the western, central and eastern portions of the border, the Defense Ministry official said. The trees will stay lit for 15 days starting Dec. 23.

Animosity between the two Koreas still lingers in the aftermath of the North’s alleged torpedoing of a South Korean warship and its artillery bombardment of a South Korean island that killed a total of 50 South Koreans last year. North Korea has denied responsibility in the warship sinking.

The two Koreas fought a devastating three-year war in the early 1950s. The war ended in an armistice, not a peace treaty, leaving the Korean peninsula technically in a state of war.