SEOUL, South Korea — North Korea fired its sixth missile in three days, demonstrating its military capabilities in defiance of global sanctions and diplomatic efforts to convince the totalitarian state to return to talks.

Kim Jong Un’s regime fired a projectile into waters off its eastern coast between 11 a.m. and noon and another between 4 p.m. and 5 p.m. Monday, South Korean Defense Ministry spokesman Kim Min Seok said in Seoul.

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The North, which launched a short-range missile yesterday after firing three on May 18, Monday said it is exercising its right to test-fire rockets as part of regular military drills.

The launches follow months of North Korean threats that have moderated since the United States and South Korea intensified diplomatic efforts this month to ease tensions and boost Chinese participation in global sanctions that target the North’s nuclear weapons program. The North has warned of nuclear strikes since testing an atomic device in February.

While the South sees no unusual North Korean troop movements, the military is “closely monitoring the situation” and is ready to respond to any escalation, Defense Ministry spokesman Kim said. Earlier this month, the North threatened to retaliate against joint U.S. and South Korean naval drills.

“The North is likely testing these missiles as an armed protest against the recent military drills jointly conducted by the U.S. and South Korea,” said Yang Moo Jin, a professor at the University of North Korean Studies in Seoul.

Kim’s regime tested an atomic weapon in February, then threatened preemptive nuclear strikes against South Korea and the United States in retaliation for annual drills that ended last month. The warnings led the United States, South Korea, and Japan to boost defenses and raised concern in China, the North’s biggest ally.

“Safeguarding peace and stability on the Korean peninsula is inevitable and what everyone wants,” Chinese Foreign Ministry spokesman Hong Lei said Monday. “We hope under the current circumstances all parties will do things that will ease tensions and improve relationships.”

Rocket Range

North Korea’s Musudan rocket has a range of 3,000 miles (4,827 kilometers) to 3,500 miles -- which is a potential threat to Guam, a U.S. territory, though not to Hawaii or the U.S. mainland, according to testimony before Congress given in April by Admiral Samuel Locklear, head of the U.S. Pacific Command.

The North doesn’t have the ability to launch a nuclear-armed missile, President Barack Obama said on April 16.

“Using short-range missiles is a relatively restrained move by North Korea’s standards,” Willy Wo-Lap Lam, an adjunct professor of history at the Chinese University of Hong Kong, said by phone May 18. “Unlike in April when it was sending out hostile messages almost every day, North Korea has been more restrained in the past few weeks.”

While the Obama administration has said it would seek to increase pressure on North Korea should it test a missile or nuclear device, previous United Nations measures have failed to deter the Kim regime.

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The U.N. Security Council twice this year tightened existing penalties passed in 2006 and 2009 against weapons development, financial transactions and travel.

Talks for Aid

South Korea Sunday urged the North to accept its calls for working-level talks on bringing completed goods to the South from the Gaeseong industrial zone, according to Unification Ministry spokesman Kim Hyung Suk.

The North demanded that the South express its willingness to resolve a dispute over the zone, according to a statement carried Monday by KCNA.

The jointly run factory park in the North Korean border city of Gaeseong has been shuttered since the North decided on April 8 to withdraw all its workers from the complex.

The United States and South Korea have repeatedly called on China, the North’s biggest trading partner, which has shielded the nation from stronger United Nations actions, to make greater efforts to enforce sanctions targeting the North’s nuclear weapons program.

A Chinese state bank closed the account of a North Korean lender earlier this month, signaling a possible change in stance.