SEOUL, South Korea—North Korea has conducted artillery firing exercises to bolster its defense capability, state media reported Sunday, its latest weapons test as Pyongyang continues to pressure Washington and Seoul to abandon what it calls their hostile policy. An artillery firing competition among mechanized units was held on Saturday, with senior government and military officials present, the official Korean Central News Agency reported. Leader Kim Jong Un was not mentioned in the report, suggesting he did not observe the training. He supervised a similar artillery firing drill last year. Since September, North Korea has test-launched a series of newly developed missiles, including nuclear-capable weapons that place U.S. allies South Korea and Japan within striking distance. Some experts say North Korea wants its rivals to accept it as a nuclear power state and work to ease international sanctions on the country. The North’s artillery tests draw less outside attention than its …