China's top lawmaking body has announced a three-day session for the end of this month, a move that raises the possibility of the enactment of a national security law for Hong Kong that has stirred debate in the semi-autonomous territory.

The official Xinhua News Agency said Sunday that the Standing Committee of the National People’s Congress would meet from June 28-30 in Beijing. The timing of the meeting is unusual, coming just one week after a three-day session that ended Saturday. The NPC Standing Committee typically meets every two months.

China plans to establish a special bureau in Hong Kong to investigate and prosecute crimes considered threatening to national security, according to details of a controversial new national security law Beijing is imposing on the semi-autonomous territory. In addition, bodies in all Hong Kong government departments, from finance to immigration, will be required to answer directly to the central government in Beijing, the official Xinhua News Agency said Saturday.

The announcement increases concerns that China’s communist government will continue to tighten its grip on Hong Kong. Beijing has said it is determined to press ahead with the national security legislation — which has been strongly criticized as undermining the Asian financial hub's legal and political institutions.

An unofficial referendum organized by a coalition of 30 trade unions and student organizations calling for strike action over Beijing's new national security law failed to get the desired results on Sunday. Just 9,000 votes were cast by union members, meaning that the vote fell short of the 60% needed to initiate strike action.