Premier Li Keqiang has urged Philippine President Benigno Aquino to resolve the row over the Manila bus hostage crisis as soon as possible, taking the impasse to a new diplomatic level.
Families of the victims and political analysts described it as a "breakthrough" and believed it would put pressure on the Philippines.
But one observer noted that given the tensions between the two countries over territorial claims in the South China Sea it might not have an immediate impact.
According to a report by the China News Service, Li had a brief conversation with Aquino in a VIP room during the East Asia Summit on Wednesday.
Li said the incident had "dragged on for long" enough and had "affected the feelings of the people in China, especially the compatriots in Hong Kong", the report said. Li said he hoped the Philippine government would resolve the incident reasonably and fairly.
Aquino said a probe carried out by the Philippines was continuing and the Philippines would strive to handle the incident properly.
Li also explained to Aquino China's principles and stance over their sovereignty dispute in the South China Sea, the report said.
The conversations took place after Chief Executive Leung Chun-ying told Aquino during a 40-minute meeting on Monday night that unless the matter was resolved properly it would continue to stand in the way of normal relations between Hong Kong and the Philippines.
Aquino agreed that ministerial meetings should take place as soon as possible to discuss how to follow up the matter, but refused to apologise.
The hostage tragedy happened in August 2010 when policeman Rolando Mendoza took 22 Hongkongers hostage on a tour bus and shot eight dead before being killed himself.
Tse Chi-kin, elder brother of slain tour guide Masa Tse Ting-chunn, said it was a breakthrough that the premier talked to Aquino in a forceful way.
"It is definitely a good thing. In the past three years, the president [Aquino] has not respected us at all," Tse said.
Democratic Party lawmaker James To Kun-sun, who has been assisting victims' families, interpreted Li's remarks as a warning to the Philippine government.