In Korea's Demilitarized Zone: Watching them, watching us

(CNN) -- A North Korean soldier lifts his binoculars, watching us watching him.

He is a matter of meters away from the border between North and South Korea in the DMZ, or Demilitarized Zone -- ironically named as it is considered one of the most heavily-fortified borders in the world.

Between us stand the blue huts of the Joint Security Area, where countless negotiations have been held between the North, the South and the U.S. since 1953 when the Armistice was signed, ending the Korean War.

The border itself here is inauspicious: A slim concrete ridge raised just a few inches from the ground -- a simple slab divides one people into two diametrically opposed countries.

North and South Korean soldiers often face off across this border. There have been many bloody skirmishes over the years, but today both sides appear keen to avoid any misunderstandings or increase in tensions. Once we have our pictures, we, the media, are moved along quickly.

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The South Korean military has raised its level of alert since Kim Jong Il's death. The U.S. military will not be drawn on its own level.

"We are maintaining a level of readiness that is expected of us on any given day in the Republic of Korea," says Colonel Jonathan Withington, spokesperson for U.S. Forces in Korea, adding, "We have seen no unusual activity."

The DMZ runs along the 38th parallel which divides the Korean peninsula roughly in half. The buffer zone is 250kms (160 miles) long and 4kms (2.5 miles) wide.

Monitoring along this border will inevitably have been stepped up in the wake of the death of North Korean leader Kim Jong Il -- potentially on both sides.

But for the U.S. and South Korean militaries, this limited view from the DMZ -- and satellite surveillance imagery -- are among the best bets for scrutinizing the most secretive and restricted country in the world.

Little wonder that both countries learned of the Dear Leader's demise not from their own intelligence agencies but from an emotional North Korean TV announcement.