A worker at the British consulate in Hong Kong has been given 15 days of administrative detention in the city of Shenzhen for violating a law on public order, China has said.

At a daily briefing on Wednesday, foreign ministry spokesperson Geng Shuang said the case was "not a diplomatic issue."

He said the man had violated regulations on "Punishments in Public Order and Security Administration," but gave no further details.

The British foreign ministry has said it is "extremely concerned" about its staff member, identified by local media as Simon Cheng Man-kit, a trade and investment officer at the Scottish Development International section of the consulate.

Reports have said he attended a business event in Shenzhen on 8 August but never returned to neighbouring Hong Kong despite plans to do so the same day.

Continuing protests rock Hong Kong: In pictures Show all 35 1 /35 Continuing protests rock Hong Kong: In pictures Continuing protests rock Hong Kong: In pictures Police officers point their guns towards pro-democracy protesters after a clash at a march in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures Pro-democracy protesters throw molotov cocktails during clashes with riot police in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures Demonstrators rally behind barricades ass they are shrouded in tear gas deployed by police in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures Police clash withpro-democracy protesters at a march in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures A police officer prepares to strike a protester as clashes erupt during a pro-democracy march in Hong Kong on August 24 AFP/Getty Continuing protests rock Hong Kong: In pictures A water cannon is fired by riot police to clear the street of demonstrators during a protest in Hong Kong on August 25 EPA Continuing protests rock Hong Kong: In pictures Pro-democracy protesters use a slingshot during clashes with riot police in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures Riot police fire tear gas to disperse pro-democracy protesters in Hong Kong on August 24 Reuters Continuing protests rock Hong Kong: In pictures A demonstrator throws a molotov cocktail as they clash with riot police during a protest in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures A demonstrator swings a tennis racket in an attempt to knock back a tear gas cannister thrown by riot police during a protest in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures A protester displays a Hong Kong Independence flag during a pro-democracy march in Hong Kong on August 24 EPA Continuing protests rock Hong Kong: In pictures Riot police tend to a detained demonstrator who has been injured during a protest in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures A demonstrator uses bamboo poles to build a barricade during a protest in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures Riot police clash with demonstrators during a protest in Hong Kong on August 24 Reuters Continuing protests rock Hong Kong: In pictures Protesters are hit by tear gas fired by the police in Hong Kong on August 24 AFP/Getty Continuing protests rock Hong Kong: In pictures Demonstrators shrouded in tear gas shield themselves behind barricades during a clash with riot police in Hong Kong on August 25 Getty Continuing protests rock Hong Kong: In pictures Riot police arrest a protester during a pro-democracy march in Hong Kong on August 24 EPA Continuing protests rock Hong Kong: In pictures Police clash with pro-democracy protesters at the Hong Kong international airport on August 13 AFP/Getty Continuing protests rock Hong Kong: In pictures Protesters fall back as they clash with police during a protest at Kowloon Bay in Hong Kong on August 24 AFP/Getty Continuing protests rock Hong Kong: In pictures Police clash with pro-democracy protesters at the Hong Kong international airport on August 13 Reuters Continuing protests rock Hong Kong: In pictures Riot police move to disperse protesters during a clash at the Hong Kong international airport on August 13 Reuters Continuing protests rock Hong Kong: In pictures Commuters riding in a bus drive past protesters in Hong Kong's Kowloon Bay on August 24 AFP/Getty Continuing protests rock Hong Kong: In pictures Protester hold umbrellas as they take part in a pro-democracy march in Hong Kong on August 24 EPA Continuing protests rock Hong Kong: In pictures Riot police detain a demonstrator as they clash during a protest in Hong Kong on August 24 Reuters Continuing protests rock Hong Kong: In pictures Pro-democracy protesters block the entrance to the airport terminals after clashes with police at the Hong Kong international airport on August 13 AFP/Getty Continuing protests rock Hong Kong: In pictures Riot police spray pepper spray as shield themselves by a police van during a clash with pro-democracy protesters at the Hong Kong international airport on August 13 Reuters Continuing protests rock Hong Kong: In pictures Riot police use pepper spray to disperse protesters during a demonstration at the Hong Kong international airport on August 13 Reuters Continuing protests rock Hong Kong: In pictures Demonstrators shrouded in tear gas shield themselves behind barricades during a clash with riot police in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures Medical professionals gather to protest police brutality at the Queen Elizabeth Hospital in Hong Kong on August 13 Getty Images Continuing protests rock Hong Kong: In pictures Police detain a pro-democracy protester at the Hong Kong international airport on August 13 AFP/Getty Continuing protests rock Hong Kong: In pictures A protester is halted by police during an occupation at the Hong Kong international airport on August 13 AP Continuing protests rock Hong Kong: In pictures Police clash with pro-democracy protesters at the Hong Kong international airport on August 13 AFP/Getty Continuing protests rock Hong Kong: In pictures Police stand guard at the entrance of the departure terminals at the Hong Kong international airport on August 13 AFP/Getty Continuing protests rock Hong Kong: In pictures Protesters continue their occupation at the Hong Kong international airport on August 14 AP Continuing protests rock Hong Kong: In pictures Travellers read placards and posters left by pro-democracy protesters at the Hong Kong international airport on August 14 AP

It is unclear whether the man possessed a diplomatic passport. Mr Geng said he was a Hong Kong resident and not a UK citizen.

Public order and security infractions are generally minor — for instance, fighting on the street — and result in administrative rather than criminal punishments.

The maximum penalty for such transgressions is 15 days in detention.

The seizure of consular staff of any status or rank is highly unusual. Despite Beijing's declaration of a "golden era" in Sino-British ties, relations have grown tense in recent months amid pro-democracy protests in Hong Kong, a former British colony.

"Regarding the series of words and deeds by the British side recently on Hong Kong-related issues, we have repeatedly lodged solemn complaints with the UK," Mr Geng said, adding that China urges the UK to "stop meddling in Hong Kong affairs."

Hong Kong Senior Police Superintendent Kong Wing-cheung said on Tuesday that Hong Kong law enforcement agencies were not notified about the case by mainland Chinese authorities under a mutual notification arrangement set up for such cases.