SINGAPORE - After having five bottles of beer at a Geylang coffeeshop, a 31-year-old construction worker from China called the police hotline and threatened to cause an explosion at Parliament House.

He also threatened to attack the family of the police staff sergeant who was speaking to him, if he was not put through to the Istana.

On Wednesday (March 9), Zhang Quanfu was jailed for 28 weeks after he admitted to two charges under the Telecommunications Act.

The court heard that Zhang went drinking with two friends in Lorong 27 Geylang at about 3pm on July 19 last year.

At 5.39pm, he left his friends and called the police emergency hotline from a mobile phone.

Speaking in Mandarin, he told the police: "I will let the Parliament building explode immediately."

A senior staff sergeant tried to keep Zhang talking on the line while he dispatched multiple police officers at the same time.

While the officer was still talking to him, Zhang used another mobile phone to call the 999 hotline again at 5.52pm.

This time, he said: "I immediately, want you to get me a line through to the Prime Minister's home, do you believe, I will wipe out (your) whole family immediately."

Zhang also told the staff sergeant, who took the second call, that he was in between Lorong 24 Geylang and Lorong 26 Geylang, and was dressed in a white T-shirt and jeans.

He also gave his name to the police, before hanging up at 6.04pm.

Another police sergeant called him back, to keep him on the line, while police officers were dispatched to Geylang.

A police corporal spotted Zhang there at 6.19pm. He was using his mobile phone and reeking of alcohol.

Zhang ignored the policeman when he was asked for his particulars.

The officer took the phone away from him and spoke directly to the sergeant on the other line, who confirmed that Zhang had made the 999 calls.

He was taken to Bedok Police Division Headquarters and arrested later that day. His blood sample found a high level of ethanol - 139mg per 100ml of blood.

Deputy Public Prosecutor Ryan David Lim told the court: "In actuality, the accused had no intention to cause any building to explode, and had no means of creating a bomb or any other explosive device.

"As a result of the accused's actions, several police resources were dispatched and others were asked to increase patrols at sensitive locations and to heighten vigilance."

In mitigation, Zhang said he was deeply remorseful and that his family back home was very worried about him. He pleaded for a light sentence so that he could go home as soon as possible and be reunited with his family.

The maximum punishment for transmitting a false message which contains a reference to an explosion is seven years jail and a $50,000 fine.

The maximum penalty for transmitting a false message is three years' jail and a $10,000 fine.

Correction note: An earlier version of this article stated that Zhang had threatened to attack the Prime Minister's family. This is an incorrect translation of his message in Mandarin. We are sorry for the error.