Toy balloons released by kindergarten children sparked a security alert in South Korea amid growing military tensions with North Korea, the defence ministry said today.



Troops and police mobilised a special task force early yesterday after a resident of Ansan, 35km southwest of Seoul, reported that 40 to 50 flying objects resembling parachutes fell on a mountain the previous night.



They turned out to be balloons from a nearby kindergarten, a ministry spokesperson said.



An explosion on June 7 on Yeonpyeong Island, near the sea border with North Korea, along with the discovery of a diving suit on the island’s shoreline, also sparked an alert.



A joint military and police investigation found that the diving suit was abandoned by a fisherman and the explosion was not suspicious.



State inspectors strongly criticised military chiefs for their inadequate response to the sinking of a warship near the disputed sea border on March 26, with the loss of 46 lives.



The inspectors recommended that 13 generals, 10 lower-level officers and two civilian defence ministry officials be punished.



The country’s top military officer Lee Sang-Eui offered his resignation.



South Korea announced reprisals against North Korea after a separate multinational investigation concluded that a submarine from the North had torpedoed the warship.