The 239 people on board included 153 Chinese citizens, and Li told his once-a-year press conference: "Those people's families and friends are burning with anxiety."
"The Chinese government and the Chinese people are all deeply concerned about their safety," he said.
"We are all eagerly awaiting news about the plane, even the slightest piece of good news."
China had eight ships taking part in the search efforts, with a ninth on its way, and had deployed 10 satellites, he said.
AFP