The incident happened at around 1pm as the courthouse heard the landmark national security case against 47 democracy advocates.

The police said it was not yet clear as to what struck the window, and officers are currently canvassing the area looking for the projectile.

No one was injured in the incident, while the alleged shooting left the 2 by 5-meter glass window cracked, with a tiny hole in it.

It is understood that a courthouse security guard heard a popping sound this afternoon and later noticed the window "spidered," meaning that the shatter-proof glass was cracked but intact after being struck by a projectile.

Secretary for Justice Paul Lam Ting-kwok strongly condemned the violent acts that intended to disrupt or damage the due administration of justice.

”The government will seriously pursue any offender who disrupts social order and undermines the rule of law, and will spare no effort in bringing the culprit to justice,” he added in the statement.

A judiciary spokesman said that given a key trial is being heard at West Kowloon Magistrates’ Courts, the judiciary has stepped up with security arrangements in the building.