Chinese state-run Xinhua news agency previously reported the law would criminalize offenses such as secession, subversion against the central Chinese government, terrorism, and colluding with foreign forces.
A draft of the law had not been made public ahead of its passage, meaning the majority of people in Hong Kong have not seen details of a law that will now govern their lives.
The passing of the law has not been officially confirmed and details remain unclear. But RTHK reports that possible maximum sentencing for crimes under the law will be "much higher" than 10 years imprisonment.
Hong Kong's Chief Executive Carrie Lam refused to comment on the progress of the bill in her weekly press conference on Tuesday morning, saying it would be "inappropriate" to respond to questions while the NPC meeting is still in progress.
The legislation was widely criticized by opposition lawmakers in Hong Kong, human rights groups and politicians worldwide, with many saying the law will cement Beijing's direct control over the semi-autonomous city. Many worry the law could be used to target political dissidents, a fear that stems from China's judicial track record.
The passing of the law comes a day before July 1, the anniversary of Hong Kong's handover from British colonial rule to China in 1997. It has become an annual day of protests in the city, but for the first time since handover police have not given permission to protesters to hold peaceful demonstrations.
The law's passing is expected to fuel further anger and protests in the city, which was rocked by over six months of increasingly violent anti-government unrest last year.
Crucially, those freedoms include the right to assembly, a free press, and an independent judiciary, rights that are not enjoyed on the Chinese mainland.
Chinese officials and state media have defended the law as vital to protecting national security in the wake of last year's protests and a 17-year failure by the Hong Kong government to pass similar legislation, since the last effort was met with mass protests in 2003.
In a blueprint of the law revealed by Chinese state media Xinhua on June 22, the law will allow mainland Chinese officials to operate in Hong Kong for the first time and give Beijing the power to override local laws.
According to the blueprint, the law will allow Beijing to establish a national security office, staffed by mainland security services to supervise local authorities in policing the law. A national security commission will also be set up, with a Beijing-appointed adviser and operating under "the supervision of the central government."
Additionally, Hong Kong's top official, the Chief Executive, will pick which judges hear national security cases, while mainland Chinese authorities will be able to "exercise jurisdiction" over cases in special circumstances -- a controversial clause that raises the prospect that certain crimes in Hong Kong could result in trials on the mainland.
Ultimately, the blueprint makes clear that national security law trumps local laws. If there is a conflict with existing Hong Kong law, the national security law will prevail.
He said Hong Kong "will continue to fight for our freedoms and democracy for the city's next generations. When justice fails, our fight goes on."
Rights group Amnesty International said the legislation "represents the greatest threat to human rights in the city's recent history."
"From now on, China will have the power to impose its own laws on any criminal suspect it chooses," said the head of Amnesty International's China Team, Joshua Rosenzweig.
"The speed and secrecy with which China has pushed through this legislation intensifies the fear that Beijing has calculatingly created a weapon of repression to be used against government critics, including people who are merely expressing their views or protesting peacefully," he said.
"As Beijing moves forward with passing the national security law, the United States will today end exports of US-origin defense equipment and will take steps toward imposing the same restrictions on US defense and dual-use technologies to Hong Kong as it does for China," Pompeo said. "The United States is forced to take this action to protect US national security. We can no longer distinguish between the export of controlled items to Hong Kong or to mainland China."
This is the first action the US government has taken to upend the special status trade relationship between the US and Hong Kong, following the determination that Hong Kong was no longer autonomous from China due to Beijing imposing the national security law on the city.
This is a developing story