Homemade bombs, or improvised explosive devices, have left scars on many world cities, as such deadly weapons are the hallmark of terrorist attacks.

So when the Hong Kong police said two IEDs were found on a train arriving at Hong Kong's Lo Wu station on Sunday, it should prompt the special administrative region to maintain the highest degree of vigilance.

The bombs were found after wires were spotted inside a plastic bag that had been placed under a seat on a mass transit rail train from Kowloon to Lo Wu in the New Territories, where the station links to a checkpoint on the boundary with the Chinese mainland.

The police cordoned off the site and called in the bomb squad who determined there were two explosive devices inside the bag. Alick McWhirter, a senior bomb disposal officer, said the bombs were viable.

The bombs mean the city is "one big step closer to terrorism", as those who planted the device apparently aimed to vandalize the train service connecting Hong Kong to the Chinese mainland even at the cost of human life.

According to the police, someone claimed responsibility on an online platform and threatened to place more bombs in public places if the boundary wasn't closed.

The user claimed that "planting bombs was easy" and that mainlanders should consider their personal safety when visiting Hong Kong. Similar claims were made after a homemade bomb was found in a hospital in Hong Kong on Jan 27.

This is now the fourth time IEDs have been found in Hong Kong in a short period of time.

Hence, there is enough evidence to show that some in Hong Kong are willing to go to extreme lengths to sow fear among the city's residents.

The bomb threats have also served to further damage Hong Kong's economy. In the past few months, the violent upheavals that have plagued the city have taken a heavy toll on Hong Kong's economy and its people's livelihoods, and the bomb threats have only compounded the downward pressure.

Nevertheless, Hong Kong, with the strong backing from the mainland, will not be daunted by such threats. Under such circumstances, the SAR government and the police should do whatever needs to be done to hunt down those who are planting the explosive devices in the city and plug every loophole that threatens public security.

Anyone who dares to use terrorist weapons against their own fellow citizens in Hong Kong will be the enemy of all Chinese people.