A military expert said the visit by two PLA naval vessels to Hong Kong is a good opportunity to demonstrate China's military advances.

The training vessel Qi Jiguang and the landing ship Yimengshan arrived in the SAR on Tuesday for a four-day port call.

The visit is also part of the celebrations marking the 76th anniversary of the founding of the People's Republic of China.

Speaking on RTHK's BackChat programme, Zhou Bo, a senior fellow at the Centre for International Security and Strategy at Tsinghua University and a retired PLA senior colonel, said while there are already PLA naval ships with a permanent presence in Hong Kong, the training and landing vessels are much bigger in size.

"(For) the amphibious landing ship, Yimengshan... tanks and armoured vehicles could be stored inside, and these are actually big ships that could carry heavy combat platforms during an assault," he said.

Zhou said the presence of the ships in Hong Kong on National Day demonstrated China's military strength and overall growth.

"The PLA Navy now happens to be the largest navy in terms of the number of ships, but not in terms of tonnage," he said.

"In terms of tonnage, the US Navy is still the world's largest, but right now, having the largest number of ships matters tremendously in naval warfare.

"And nowadays, as the Chinese navy becomes more and more modern, it's also becoming more sophisticated and more involved in the blue water operations in the world."

Zhou also said the port call enhances the bond between Hong Kong and the mainland, while highlighting the country's commitment to peaceful development.

"Hong Kong people should rightly feel that they are part of the big family, which is getting stronger and stronger... and that makes people feel proud.

"But having said that, it doesn't mean that being strong, you would necessarily become assertive and aggressive. These are two different things.

"What one can see is a kind of military capability that's also showcased at Tiananmen Square [in the Victory Day Parade on September 3], but you don't have to make use of that capability unless it's absolutely necessary."