South Korea's share in the Chinese, U.S. and European auto markets has been declining for the past four years amid tense competition from Japanese and American automakers, industry sources said Thursday.

South Korea's share of the global auto market stood at an average 5.8 percent in the three major markets during the first five months this year, the sources said.

The numbers have been falling steadily from 7.7 percent in 2012 to 7.5 percent in 2013 and 2014, and 7.2 percent in 2015. Last year's market share stood at 7.1 percent.

In the Chinese market, South Korea's share peaked at 9 percent in 2014 before falling to 7.9 percent in 2015, 7.4 percent in 2016 and 4 percent for the first five months this year.

The sharp drop this year is attributed to the Chinese government retaliating economically against South Korea's deployment of the US anti-missile system THAAD on its soil despite Beijing's strong objection.

South Korea's US auto market share also shrank to 7.6 percent for the first five months this year from 8.9 percent in 2011 and 7.9 percent in 2014.

The comparable figure for the European market hovered between 5.7 and 5.9 percent for the past six years.

Analysts called on the South Korean government and the auto industry to join forces to invest more in research and development on cutting-edge technology and enhance effectiveness in auto production to catch up with Japanese and US automakers.

"The South Korean auto industry should also try to maintain its firm status in the advanced economies rather than eyeing only emerging markets," Lee Hang-koo of the Korea Institute for Industrial Economics and Trade said. "South Korea's auto industry is on the verge of losing growth momentum and heading toward a critical phase." (Yonhap)