All reserve forces for disaster relief should be on stand-by 24 hours everyday to provide possible support for disaster areas.
Li urged strengthening the cooperation between central and local governments, so as to ensure scientific, effective, orderly and vigorous disaster-relief work.
He odered releasing accurate information on the disaster situation, quake-relief work as well as death toll and injuries in a timely manner so as to boost people' s confidence and thus make them reassured.
He also demanded preparation for post-disaster reconstruction work.
"We once underwent catastrophes and have experience in dealing with them. We have quite a fine emergency response system," Li said, adding that "under the strong leadership of the Party and government, and as long as we unite as one and conduct rescue work scientifically, we are able to minimize the losses and overcome the disaster."
Earlier in the day, Chinese President Xi Jinping ordered all-out efforts to rescue victims and minimize deaths and injuries.
The State Council, or the cabinet, has launched a first-grade emergency response to the earthquake. Emergency teams of ministries, armed forces and armed police are heading to the quake zone.
The epicenter, with a depth of 13 km, was monitored at 30.3 degrees north latitude and 103.0 degrees east longitude.
Ya'an has a population of 1.53 million and is known as the hometown of the giant panda. It is about 140 kilometers away from the provincial capital Chengdu City.
Rescue efforts under way after SW China earthquake