This photo released by North Korea's state-run Korean Central News Agency on July 26 shows a missile being launched from a site near the North's eastern coastal town of Wonsan the previous day. KCNA-Yonhap

North Korea's recent missile launches appear to be aimed at displaying discontent with next month's joint military exercise between South Korea and the United States and strengthening its negotiating power before resuming nuclear talks with the United States, experts said Wednesday.

Wednesday's launches of two short-range ballistic missiles off the east coast marked the second time in less than a week that the communist nation has fired missiles. Experts warn that yet more missile launches could take place until the exercise, codenamed "19-2 Dong Maeng," is over.

"The fact that the missiles were short-range and flew at a low altitude tells us that the test-firing was directed at the South," Nam Chang-hee, a professor at Inha University said. "The North is obviously not happy about our efforts to keep the balance of terror as we keep the military drills in place and have decided to bring in F-35 stealth fighter jets."

North Korea has long denounced joint military drills between South Korean and U.S. forces as a rehearsal for invasion. Seoul and Washington reject the claim, arguing that such maneuvers are purely defensive in nature.

After last week's missile firings, the North's state media said that the launches were designed to send a "solemn" warning to South Korea over its plan to conduct joint military drills with the U.S. and purchase the high-tech fighter jets from the ally.

"It is to put pressure on Seoul since it has not changed its stance about the drills, and raise tensions by showing off its military capabilities," Yang Moo-jin, a professor at the University of North Korean Studies, said.

President Donald Trump speaks to the press about how U.S. and Guatemala have reached an agreement on asylum in the Oval Office of the White House in Washington, DC on Friday, July 26, 2019. The President was joined by Guatemalan minister Enrique Degenhart and Acting Secretary of Homeland Security Kevin K. McAleenan who signed a written agreement. During questions from the press he spoke about tariffs on French wine, North Korea's short range missiles and his vacation plans. UPI-Yonhap

Given that the missiles fired since last week flew at low altitudes of 50km and 30km, respectively, they demonstrate that the North has been improving its missile technology to an extent that they can't be easily intercepted, experts said.

Last week's missiles, fired on Thursday, ascended again in the final downward stage of ballistic trajectory, an advanced capability, known as a "pull-up" maneuver, which makes it difficult for interceptors to shoot down such missiles.

South Korean military officials said that Wednesday's missiles appear to be a similar type to those launched last week that have been identified as "KN-23," or the North's version of Russia's Iskander ballistic missile.