North Korea fired three short-range ballistic missiles into the sea off its east coast early Saturday, South Korea and the US military said, reviving tensions with Washington after President Donald Trump had said Pyongyang was starting to show some "respect". The launches come as tens of thousands of South Korean and US troops take part in joint military drills in the south of the peninsula, which the North denounces as preparation for war and as highly provocative. Following an initial US assessment saying that two of the missiles had "failed in flight", a spokesman for the US Pacific Command later said the two weapons had not failed but "flew approximately 250 kilometers in a northeastern direction". One of the three missiles blew up "almost immediately", with none of the weapons posing a threat to either North America or the US territory of Guam, the spokesman said. The South Korean Office of the Joint Chiefs of Staff said the projectiles were launched from the Norths eastern Kangwon province into the sea. Lee Il-Woo, an analyst at Korea Defence Network, said the launches represented a "low-level provocative act" carried out in response to the US-South Korea exercises, which are seen by Pyongyang as a rehearsal for an invasion of its own territory. The joint exercises started Monday at a time of heightened tensions between Pyongyang and Washington, after two successful intercontinental ballistic missile (ICBM) launches carried out by North Korea last month apparently brought most of the United States into range for the first time. Analyst Yang Uk at the Korea Defense and Security Forum told AFP the latest launches by Pyongyang were "carefully calibrated... to avoid revving up tensions too high beyond its control". The launches, which took place over a span of 30 minutes, came as North Korean state media reported that leader Kim Jong-Un oversaw a military exercise simulating a special forces assault on South Korean border islands involving aircraft, "multiple-missile launchers" and howitzers.  North Koreas ICBM launches last month triggered an intense warning by Trump that Washington could rain "fire and fury" on the North. Pyongyang then threatened to fire a salvo of missiles towards the US territory of Guam, but later backed away from the plan and tensions had eased. Trump said Wednesday that Kim Jong-Un was "starting to respect" the United States, hours after Secretary of State Rex Tillerson said talks with the nuclear-armed North over its banned weapons programs might be possible "in the near future". White House press secretary Sarah Sanders said Saturday that Trump was aware of the launches. "In regards to activity in North Korea tonight, the president has been briefed and we are monitoring the situation," she said.