North Korea fired a ballistic missile towards the Korean Peninsula’s east coast on Sunday, South Korea’s military said.

The North’s missile launch comes just days after the country tested a high-thrust solid-fuel engine that experts said would allow quicker and more mobile launch of ballistic missiles, as it seeks to develop a new strategic weapon and speed up its nuclear and missile programmes.

The test, overseen by leader Kim Jong Un, was conducted on Thursday at North Korea’s Sohae Satellite Launching Ground which has been used to test missile technologies, including rocket engines and space launch vehicles, the official KCNA news agency reported on Friday.

North Korea has conducted an unprecedented number of missile tests this year, including an ICBM capable of reaching the U.S. mainland, despite international bans and sanctions.