Patience with North Korea has snapped among many South Koreans and a martial mood is spreading among its leaders, military brass and people after Pyongyang's deadly artillery strikes last week.

Reflecting the popular sentiment, a grim-faced President Lee Myung-Bak in a national address Monday described the strikes "inhumane" and vowed to "make the North pay the price" for any further provocations.

Over the years Seoul has fumed, but usually refrained from retaliating, as the hardline regime of Kim Jong-Il staged nuclear tests, fired long-range missiles and, just weeks ago, showed off a new uranium enrichment plant.

Most South Koreans, especially younger generations, have long shrugged off the regime's Cold War-style verbal attacks which label them "warmongers" and "the US imperialists' puppet forces".

Agents from the North blew up a South Korean airliner in 1987, killing 115 people. Pyongyang has also been blamed by a multinational panel for the March sinking of a South Korean corvette, the Cheonan, killing 46 sailors.

But many believe North Korea staged its most brazen provocation yet when it rained 80 shells and rockets on to the South's border island of Yeonpyeong last Tuesday, killing two marines and two construction workers.

The first artillery attack on a civilian area in the South since the 1950-53 war reduced two dozen buildings to smouldering ruins and sparked a panicked exodus of almost all of the island's 1,500 residents.

At the funeral for the two marines Saturday, which was broadcast across the nation, Marine Corps commander Lieutenant General Yoo Nak-Joon vowed to "repay North Korea a hundred- and thousand-fold" for their deaths.

The government has announced it would beef up island defences, reform the military and change its rules of engagement, which have so far strongly emphasised the avoidance of escalation.

Military analysts warn that another Korean war would bring a nightmare scenario of a devastated Korean peninsula and one million deaths.

Pyongyang has claimed it only retaliated last Tuesday after its "superhuman" patience had been broken by the South firing shells into waters that the North claims as its own during an artillery drill.

Many South Koreans believe it is they who have been turning the other cheek.

Korea Policy Research Centre president Yo Ho-Yeol said: "Even until the Cheonan incident, public sentiment was still divided between criticising the North and criticising our own government's hardline stance (on the North).

"But this time it was clearly the North's military attack, which even caused civilian casualties.

"So now the public sentiment is clearly dominated by anger towards the North. And a majority of the public wants strong retaliation against the North upon any further provocation."

Daniel Pinkston, Seoul office head of think-tank the International Crisis Group, said: "The South has been pretty tolerant, but how much can you tolerate? I don't know what the red line is, but if you don't retaliate, this is giving a green light to North Korea."

Many people strongly support a joint US-South Korean naval exercise under way which is spearheaded by an American aircraft carrier, even as Pyongyang warned that the drill brought the Koreas closer to "the brink of war".

A rally against the drill outside a naval base drew just 20 activists Sunday, with protesters holding a banner that read: "Stop the Korea-US drill that causes a vicious cycle of retaliation and confrontation!"

Their numbers have been dwarfed by far larger anti-Pyongyang rallies.

A leading North Korea expert, Peter Beck, told AFP that it might be time for South Korea to consider military action beyond its limited response to the attack, when it lobbed back artillery but shied away from air strikes.

"This attack is different than the Cheonan sinking," said Beck, currently an international affairs fellow at Keio University in Tokyo.

"There is still at least a little ambiguity about what sank the Cheonan, but this artillery strike was not only a blatant violation of the armistice agreement, it was also against civilians.

"Therefore, Seoul should consider a retaliatory strike, either on the North Korean navy or on its nuclear facilities."

Many on the streets of Seoul feel the same way.

"We should not be afraid," said 77-year-old Cheon Sang-Yong, a veteran of the Korean and Vietnam wars who now works as a part-time waiter in a fast-food restaurant. "We should be prepared to fight back."

Military balance on the Korean peninsula
Seoul (AFP) Nov 28, 2010 - More than a million troops are massed around the tense Cold War-era frontier that has bisected the Korean peninsula since the 1950-53 conflict ended in a truce and not a peace treaty.

Tensions have repeatedly flared between the communist North and the US-allied South -- most recently when the North last week launched an artillery strike on an island in the South that killed two marines and two civilians.

The United States has kept a heavy military presence in South Korea since the end of the war, in which it led United Nations forces, and remains treaty-bound to defend the South in case of attack.

North Korea has massed most of its forces and weapons near the de-facto frontier, the 250-kilometre- (155-mile-) long and four-kilometre wide Demilitarised Zone (DMZ).

In the event of a conflict Pyongyang would be expected to unleash an artillery barrage on Seoul, just 40 kilometres to the south, and then seek to invade the capital of 10 million people with troops and tanks.

North Korea follows a "military-first" policy and is believed to spend 30 percent of its GDP on defence. It has the world's fifth largest army, but US and South Korean troops have more sophisticated weapons.

Pyongyang has staged two nuclear tests and fired several long-range missiles, but it is unclear whether it can make nuclear warheads for its missiles. It is also believed to have biological and chemical weapons.

Below are the comparative military strengths of the major forces:

NORTH KOREA:

Armed forces -- around 1.2 million plus 7.7 million reserves

Tanks -- 3,900

Armoured vehicles -- 2,100

Artillery and multiple rocket launchers -- 13,600

Combat aircraft -- 840

Warships -- 420

Submarines, including midgets -- 70

Missiles -- 1,000, some with a range of more than 3,000 kilometres (1,860 miles). It has also test-launched three intercontinental Taepodong missiles

Biochemical weapons -- estimated 2,500-5,000 tons of chemical weapons, suspected capability to weaponise anthrax, smallpox and cholera

Nuclear weapons -- Most estimates say North Korea has enough plutonium to build six to eight atomic weapons.

SOUTH KOREA:

Armed forces -- 655,000 (army 522,000, navy 68,000, air force 65,000) plus about 4.5 million reservists

Tanks -- 2,300

Armoured vehicles -- 2,400

Artillery and multiple rocket launchers -- 5,400

Combat aircraft -- 490

Warships -- 140

Submarines -- 10

Guided weapons -- 30

No nuclear weapons

US FORCES IN SOUTH KOREA:

Armed forces -- 28,000

Tanks -- 50

Armoured Vehicles -- 130

Combat aircraft -- 90

Attack helicopters -- 40

Patriot and other missiles -- 100

No US nuclear weapons based in South Korea

Source for figures: South Korea's latest Defence White Paper