North Korea fired three short-range projectiles Thursday into the waters off its east coast in a possible move to stoke tensions with Seoul, a South Korean defense official said. Pyongyang’s military later criticized alleged South Korean shelling in disputed waters.

The South Korean official, who spoke on condition of anonymity because of department rules, said the projectiles flew about 190 kilometers (120 miles) before harmlessly landing in the water. The projectiles were fired from North Korea’s eastern port city of Wonsan, and the South Korean military was investigating the type of projectiles and the North’s intentions, the official said.

Later Thursday, North Korea’s army, while not mentioning its own projectiles, released a statement in state media saying South Korea had fired shells without notice into the North’s waters from a front-line island near a Yellow Sea boundary that Pyongyang bitterly disputes.

The North Korean army in the front-line area is “full of the strong will of retaliation to punish the provocateurs to the last one by giving vent to their pent-up grudge,” the statement said. “What they are waiting for is only the order to be given.”

Short-range test firings by North Korea aren’t unusual, but a barrage of missile and artillery tests earlier this year boosted animosity between the rivals. A North Korean artillery attack in 2010 killed four South Koreans on a front-line Yellow Sea island.

North Korea has in recent months threatened South Korea’s leader, calling her a prostitute, and the South has vowed to hit North Korea hard if provoked. North Korea’s rising anger coincided with annual joint military exercises by the U.S. and South Korea and a visit to Seoul by President Barack Obama. North Korea also test-fired two medium-range ballistic missiles and exchanged artillery fire with South Korea near a disputed boundary in the Yellow Sea.

On Wednesday, an unidentified spokesman for North Korea’s Foreign Ministry warned the U.S. government that if it didn’t block the release of a new American comedy about a plot to assassinate leader Kim Jong Un, it would be an “act of war.” He didn’t mention the movie by name but was clearly referring to “The Interview,” which stars Seth Rogen and James Franco.

There was also widespread speculation about a possible North Korean nuclear test. North Korea has conducted three nuclear tests since 2006, the latest in February 2013.

Experts believe North Korea has developed a handful of crude nuclear devices and is working toward building a warhead small enough to mount on a long-range missile, although most experts say that goal may take years to achieve.

The Korean Peninsula is still technically in a state of war because the 1950-53 Korean War ended with an armistice, not a peace treaty.

(AP)