"We are not targeting reporters. We are targeting national security offences," Li said.
Police said 200 officers searched the Stand News office and three men and four women, aged 34-73, were arrested on suspicion of "conspiracy to publish seditious publications".
Ronson Chan, Stand News deputy assignment editor and the head of the Hong Kong Journalists Association (HKJA), was not among those arrested but said police confiscated his computer, mobile, tablet, press pass and bank records during a search of his home.
He was seen heading back to the office after police searched his home.