The United States, South Korea, and Japan navies staged trilateral anti-submarine exercises for the first time in five years today, amid tension over North Korea's series of missile tests.<br />''<br />''According to media reports, the drills were held in international waters off the Korean peninsula's east coast.<br />''<br />''the South Korean navy in a statement has said that the exercises are designed to improve their capability to respond to increasing North Korean submarine threats, including its submarine-launched ballistic missiles.<br />''<br />''However, the US navy said, the drills will enhance inter-operability and tactical and technical coordination between the three countries.<br />''<br />''It happened just a day after North Korea fired two ballistic missiles into the sea off its east coast.<br />''<br />''<span style="color: #222222;">Thursday's test was the third such launch in five days by the North, which has fired an unprecedented number of missiles this year.</span><br />