South Korea's joint chiefs of staff said the projectile was fired off North Korea's east coast. (KCNA/EPA Images pic)

SEOUL: North Korea fired an unidentified projectile toward the sea off its east coast, South Korea's joint chiefs of staff said in a statement.

The launch came after Pyongyang's Kim Yo Jong, powerful sister of leader Kim Jong Un, issued a statement on Friday that dismissed Seoul's demand for an apology for North Korean mines that seriously wounded South Korean soldiers in the Demilitarised Zone, a heavily fortified area between the two Koreas.

South Korea said this week North Korean mines caused the blast that seriously injured two South Korean soldiers on a reconnaissance mission inside the 4-km-wide border that stretches across the Korean Peninsula.