At least four people were killed and 14 others injured after two earthquakes hit Ya'an City in southwest China's Sichuan Province, on Wednesday, halting train lines and damaging houses.

A magnitude-6.1 earthquake rattled Lushan County at 5:00 p.m., followed by a magnitude-4.5 shock three minutes later in the nearby Baoxing County of the city.

Strong tremors were felt as far as Sichuan's capital city of Chengdu and Chongqing Municipality, some Chinese social media users said online.

Sichuan fire department said some houses in Lushan County were partially damaged and it's in communication with relevant counties and towns that have been affected. 

China's railway authority has urgently halted affected sections of train lines.

Seven county-level regions in Sichuan, including five in Ya'an and two in Chengdu, face relatively high risk of geological disasters in the next 24 hours, Sichuan provincial geological disaster management office warned on Wednesday night.

The quake in Lushan was an aftershock of the 7.0-magnitude earthquake in the region in 2013, according to the Sichuan earthquake department. The 2013 quake killed 196 people and injured over 11,000.

The epicenter of the quake in Lushan, with a depth of 17 km, was monitored at 30.37 degrees north latitude and 102.94 degrees east longitude, according to the China Earthquake Networks Center.

Quick warning and rescue effort

China's disaster reduction institute in Chengdu issued a warning just four seconds after the quick in Lushan, urging tens of millions of people in the city and its surrounding towns to quickly take shelter, China Media Group reported.

The municipal government of Ya'an immediately activated a Level-II emergency response, the second highest of the four-tier system of emergency responses.

And the Chinese government activated its Level-III emergency response for earthquakes, and sent a team on site for rescue and relief operation. 

Over 1,400 provincial firefighters have been mobilized to the sites. Meanwhile, rescue teams of adjacent Guizhou, Yunnan provinces and Chongqing Municipality are prepared as reinforcements.

An amount of 50 million yuan ($4.5 million) was urgently allocated to each of the earthquake-hit Lushan and Baoxing counties for disaster relief, the Sichuan Provincial Finance Department announced on Wednesday night.

All known injured have been transferred to local hospitals for treatment.