North Korea on Sunday fired four suspected shots from multiple rocket launchers into the Yellow Sea, South Korean military officials said, the latest in a series of provocations that could heighten tensions on the Korean Peninsula.

“There were shots believed to be that of North Korea’s multiple rocket launchers this morning,” an official of the South Korean military said.

“We are maintaining our defense readiness posture while closely following related developments,” the official added.

Four shots fell into the western waters during a span of an hour from 7:20 a.m. from an unspecified location in South Pyongan Province, according to officials.

South Korea’s National Security Council held an emergency vice-ministerial meeting over North Korea’s short-range projectile launch from 9:30 a.m. for 30 minutes.

“The participants agreed to closely analyze the detailed specifications of the projectile in close cooperation between South Korea and the US, while keeping a close eye on the recent series of North Korean missile launches,” Cheong Wa Dae spokesperson Park Kyung-mi said in a statement Sunday.

She added that the Korean military would maintain a strong readiness posture to avoid a security gap in the period of government change based on strengthened capabilities of the Army and the Korea-US alliance.

This is the second provocation since the presidential election and the 11th this year. Four days ago, North Korea fired a ballistic missile presumed to be a new intercontinental ballistic missile. The missile detonated in midair at an altitude of fewer than 20 kilometers after launch.