North Korea fired a suspected ballistic missile toward the sea on Thursday, Japan said, a day after Pyongyang rejected a US decision to scale back military exercises with South Korea.

Japan’s Prime Minister’s Office said it detected the suspected launch but did not provide further details.

South Korean media, citing the military, reported that North Korea fired an unidentified projectile from its east coast.

The launch came a day after the US and South Korean militaries announced plans to reduce the scale of their 11-day Ulchi Freedom Shield exercises.

The decision followed an order from US President Donald Trump to the Pentagon to “substantially reduce” the drills. Trump cited his improved relations with North Korean leader Kim Jong Un and South Korea’s refusal to support the United States over the war in Iran.

However, Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, rejected the US move on Wednesday.

She said reducing the size and duration of the exercises would not change what she called their “provocative, aggressive nature.”

Kim Yo Jong also warned that Washington should not expect Pyongyang to view the move as a sign of goodwill.

She pointed to other military exercises conducted by the US and South Korea earlier this year and criticised South Korea’s efforts to introduce nuclear-powered submarines.