Following the measure's implementation on Saturday morning, the Shenzhen Bay Port, Hong Kong-Zhuhai-Macau Bridge and the airport, were now the only entry points to Hong Kong that remained open, the South China Morning Post (SCMP) newspaper said in a report.
As of 4 p.m. on Saturday, close to 9,000 travellers, of whom only 125 had used the Shenzhen Bay Port.
On Friday, 60,000 had entered via the same route in a frantic last-minute dash to get in before implementation.
Meanwhile, Lam who had on Wednesday announced the new measures, said that only 807 new arrivals had entered the city via the Hong Kong-Zhuhai-Macau Bridge or Shenzhen Bay, both of which were linked to mainland China.
"Many came from Macau, so they were not affected (by the measures)," Lam told the media on Saturday evening.
Lam also revealed the government had bought 48 million masks from overseas and would receive 17 million more from the mainland as it scrambled to address shortages, while admitting it was down to its last month's supply.
Public hospitals in the city were also reported to be down to a month's supply.
As of Sunday, the number of confirmed corfirmed cases in Hong Kong increased to 27.
In China, the death toll rose to 811, surpassing that of the Severe Acute Respiratory Syndrome (SARS) epidemic in 2003.
Those infected with the coronavirus - 37,198 in mainland China alone - far exceed the 8,437 SARS cases that were recorded worldwide during its outbreak.
The SARS epidemic claimed 774 lives worldwide between 2002-2003, according to the World Health Organization.