President Xi Jinping demanded that authorities quickly extinguish the fire caused by the blasts and "make full effort to rescue and treat the injured and ensure the safety of people and their property", China Central Television (CCTV) said on its official microblog.
CCTV said the blasts erupted in a shipment of explosives at around 11:30 pm local time, triggering a blast wave that was felt kilometers (miles) away. The second blast came roughly 30 seconds after the first, state media said.
The official People's Daily newspaper said the death toll was 17 while other state media said three firefighters were among the dead. The official Xinhua news agency said around 400 were hurt.
Seconds later, shockwaves hit the apartment building, causing panic among the occupants inside.
Xinhua said the explosions had ripped through a warehouse storing "dangerous goods". The first explosion was equivalent to 3 tonnes of TNT and the second blast 21 tonnes of TNT, it said.
