South Korea says it still plans to hold an artillery exercise Monday on the tiny border island of Yeonpyeong, despite threats that North Korea will retaliate.

Tensions have been running high on the peninsula since Pyongyang shelled the same island last month. The UN Security Council held a meeting Sunday in an attempt to help diffuse the situation, but failed to draft a resolution.

The one-day artillery drills are routine and defensive in nature, according to the government in Seoul. Weather will dictate when exactly marines will conduct the exercise, an officer at the Joint Chiefs of Staff told The Associated Press.

The officer, who spoke on condition of anonymity, said South Korea's military will "immediately and sternly" deal with any provocation from Pyongyang.

North Korea has warned of a "catastrophe" if the exercise takes place, saying it would act with more force than it did last month, when a barrage of artillery killed two South Korean marines and two civilians.

On Yeonpyeong island, residents, officials and journalists were ordered into underground shelters in case North Korea attacks, the officer said.

Russia called an emeregency meeting of the Security Council on Sunday in the hopes of issuing a statement about the rising tensions. After the meeting, however, Russian Ambassador to the UN Vitaly Churkin said "we were not successful in bridging all the bridges."

According to diplomats, China had strongly objected to criticizing North Korea for perpetrating two deadly attacks against its southern neighbour this year.

UN Secretary General Ban Ki-moon has called the attack on Yeonpyeong "one of the gravest provocations since the end of the Korean War."

Ban, a former South Korean foreign minister, also called Pyongyang's recent disclosure of a new uranium enrichment facility "quite alarming."

North Korea has raised the readiness levels of artillery units along the west coast, Yonhap news agency reported, citing an unidentified South Korean government official.

The official said some North Korean air force fighter jets that had been inside their hangars have been rolled out onto airstrips along the west coast, apparently ready for takeoff.

The U.S. supports South Korea, saying any country has a right to train for self-defence, but Russia and China have expressed concern.

Russia's Foreign Ministry has urged South Korea to cancel the exercises to avoid escalating tensions.

China, a key ally for the North, has said it is "unambiguously opposed" to any acts that could worsen already-high tensions.

South Korean Marines carrying rifles were conducting routine patrols on Yeonpyeong Sunday. About 240 residents, officials and journalists remain on the island, said Lim Byung-chan, an official from Ongjin County.

Amid the security jitters, nearly 800 out of 1,300 civilians living on the island moved to unsold apartments in Gimpo, west of Seoul, according to Ongjin County officials.

Several bloody naval skirmishes have occurred along the Koreas' western sea border in recent years, but last month's assault marked the first time the North has targeted a civilian area since the end of the Korean War in 1953. The North does not recognize the UN-drawn sea border in the area.

With files from The Associated Press