HAIKOU -- China's southernmost island province of Hainan issued a Level IV typhoon alert at 11:30 am on Tuesday, as a tropical depression has formed over the central South China Sea, and is expected to grow into this year's first typhoon within the next 24 hours.

It is expected to gradually move toward the eastern coast of Hainan and is likely to make landfall in the area around Friday, according to the provincial meteorological bureau.

In preparation, the maritime authority of Sansha, China's southernmost city, has also issued a warning of strong convective weather for parts of the waters around Xisha Qundao.

Since Monday, large vessels such as cargo ships and engineering vessels have been evacuated from the waters off Xisha Qundao. Smaller boats have been hoisted ashore, and professional rescue ships are on standby.

China has a four-tier flood-control emergency response system, with Level I being the highest level.