BEIJING, June 13 (Xinhua) -- China has sped up the development of clean energy and stepped up gas exploration over the past five years, a senior energy official said Thursday. Currently, clean energy sources account for 22.1 percent of total energy consumption, up from 14.5 percent five years ago, said Zhang Jianhua, head of the National Energy Administration. Coal consumption accounts for less than 60 percent of total energy use, Zhang said, adding that energy intensity has improved over the five-year period, with energy per unit of gross domestic product falling 20.3 percent. China has also stepped up oil and gas exploration to ensure energy security, he said. The country has sought to move away from coal and other fossil fuels to address pollution and foster economic development outside of the heavy industry. China has made breakthroughs in key technologies for nuclear power and unconventional oil and gas and achieved innovations in sectors such as smart grids, electric vehicles and energy big data, Zhang said. China will continue to boost the use of clean energy and expand international energy cooperation in the future, he added.