North Korea has intensified submarine drills near the tense Yellow Sea border with South Korea, putting Seoul defence officials on alert, a report said Thursday.

JoongAng Ilbo newspaper, citing a Seoul military source, said the North had been staging exercises involving five or six submarines at the Bipagot submarine base on its west coast since last month.

They feature the signature 325-tonne submarines as well as the new and bigger Shark-class submarines called K-300, it said.

"It's highly unusual for them to beef up submarine drills in March so we're intensely monitoring the situation," said the source.

Pyongyang has also started moving its military hovercraft from the northwest to a new naval base near the border to be completed in June, said another source quoted by the paper.

The new base at Koampo will make it possible for the North's troops to land via hovercraft on the South's border islands within 30 minutes, it said.

Seoul's defence minister said Tuesday the North may attempt surprise attacks across the sea border after practising marine infiltration drills.

Kim Kwan-Jin told lawmakers the drills began after the ice started to thaw. He warned of the possibility of "various types of surprise local provocations".

The disputed Yellow Sea border was the scene of deadly naval clashes in 1999, 2002 and November 2009.

The South also says a North Korean submarine fired a torpedo to sink one of its warships in March 2010 near the borderline, with the loss of 46 lives.

Pyongyang denies that attack. But last November it shelled a border island, leaving four South Koreans including two civilians dead and briefly sparking fears of war.

earlier related report
N. Korea military reserves 1 mln tons of rice: MP
Seoul (AFP) April 7, 2011 - North Korea has one million tons of rice in store for its military despite appeals for international food aid, a South Korean lawmaker said Thursday.

The rice reserve for emergencies stood at 300,000 tons for regular troops and 700,000 tons for reservists, Yoon Sang-Gyun of the ruling Grand National Party said in a statement.

"Some 300,000 tons are enough for the North's regular armed forces to continue war for 500 days," he said.

He said North Korea had also stored 1.5 million tons of oil and 1.7 million tons of ammunition for emergency use.

Yoon said his information came from intelligence authorities. The National Intelligence Service said it could not confirm this.

The legislator said the North's harvest last year increased slightly from a year earlier to 5.11 million tons.

But Pyongyang had asked other countries for aid so it could stockpile food for celebrations next year of the 100th anniversary of the birth of founding president Kim Il-Sung, he said.

The North suffered famine in the 1990s which killed hundreds of thousands and has relied partly on international food aid ever since.

But donations to UN programmes have dwindled due to international irritation at the North's missile and nuclear programmes. Seoul suspended its annual shipment of rice and fertiliser to its neighbour in 2008.

A survey of 500 North Korean refugees now living in South Korea showed that 78 percent had never received foreign food aid while in the North, according to a group called the Network for North Korean Democracy and Human Rights.

A quarter of those who had received the assistance said the North's authorities later took all or part of it away from them.

A senior Seoul official said separately that Pyongyang must accept responsibility for two deadly border incidents in return for better ties.

Chun Yung-Woo, senior presidential secretary for foreign affairs and security, said the communist state was seeking food and fertiliser ahead of 2012, along with the lifting of sanctions and massive economic aid.

"It all depends on how the North makes up its mind. It should have the courage to overcome two thresholds," Chun told a forum on the North's economy.

The South says the North must take the blame for the sinking of a South Korean warship in March 2010, and for the shelling of a border island last November, before any high-level talks are held to ease tensions.

"We cannot just put them (the incidents) behind us as if nothing had happened," Chun said.

The North angrily denies responsibility for the ship's sinking with the loss of 46 lives. It says its island attack, which killed four South Koreans including civilians, was provoked by Seoul's artillery drill.

The second threshold would be the North's abandonment of its nuclear arsenal, which Chun said would open a "totally new world" for the isolated communist state including its integration into the world community.

Yoon Duk-Min, of the Institute of Foreign Affairs and National Security, estimated that the impoverished North's newly disclosed uranium enrichment plant cost some $300-400 million.