SEOUL, KOREA, REPUBLIC OF -- A barrage of North Korean missiles fired from the ground and fighter jets splashed down on the waters off the country's east coast on Tuesday, South Korea's military said, a show of force on the eve of a key state anniversary in the North and parliamentary elections in the rival South.

The back-to-back launches were the latest in a series of weapons tests that North Korea has conducted in recent weeks amid stalled nuclear talks and outside worries about a possible coronavirus outbreak in the country.

North Korean troops based in the eastern coastal city of Munchon first launched several projectiles -- presumed to be cruise missiles -- on Tuesday morning, South Korea's Joint Chiefs of Staff said in a statement.

The weapons flew more than 150 kilometres (93 miles) at a low altitude off the North's east coast, a South Korean defence official said. If confirmed, it would be the North's first cruise missile launch in about three years, said the official, who spoke on condition of anonymity, citing department rules.

Later Tuesday, North Korea launched several Sukhoi-class fighter jets that fired an unspecified number of air-to-surface missiles toward the North's eastern waters, the defence official said.

The official said North Korea has recently appeared to be resuming its military drills that it had scaled back due to concerns about the coronavirus pandemic. He said other North Korean fighter jets also flew on patrol near the border with China on Tuesday.

All the recently tested missiles were short-range and didn't pose a direct threat to the U.S. mainland. A test of a missile capable of reaching the U.S. homeland would end North Korea's self-imposed moratorium on major weapons tests and likely completely derail nuclear diplomacy with the United States.

UN Secretary-General Antonio Guterres expressed concern at the latest missile launches by the Democratic People's Republic of Korea or DPRK, the country's official name.

"Once again we call on the DPRK leadership to comply fully with its obligations under relevant Security Council resolutions," Guterres' spokesman Stephane Dujarric said, referring to UN bans on ballistic missile launches.

The secretary-general reiterates that "diplomatic engagement remains the only path with sustainable peace and complete and verifiable denuclearization," Dujarric said.

U.S.-led diplomacy aimed at ridding North Korea of its nuclear weapons has largely been deadlocked since the February 2019 collapse of a summit between Trump and North Korean leader Kim Jong Un in Hanoi. Negotiations faltered after the U.S. rejected North Korean demands for broad sanctions relief in exchange for a partial surrender of the North's nuclear capabilities.

Some experts say North Korea likely used the latest weapons launches to bolster its striking capability against South Korea, which has been introducing U.S.-made stealth F-35 jets and other sophisticated conventional weapons systems in recent years. Others say the latest weapons tests were also aimed at shoring up internal unity in the face of U.S.-led sanctions and the coronavirus pandemic.

Go Myong-Hyun, an analyst at the Seoul-based Asan Institute for Policy, said North Korea also wants to maintain tensions to secure leverage over the U.S. in future negotiations.

"North Korea wants to create and maintain tensions, but still aims to prevent those tensions from growing too much and pressuring the U.S. a lot," Go said.

Cruise missiles fly at a lower altitude and slower speed than ballistic missiles, making them easier to intercept, but they are still considered more accurate. UN Security Council resolutions ban North Korea from engaging in any ballistic activities, but not cruise missile tests.

If the cruise missiles tested on Tuesday were newly developed weapons, they would still present a challenge to the South Korean and U.S. militaries, Go said. South Korea's military said it was analyzing details of the launches. The launches came a day before North Korea marks the 108th birthday of the country's late founder, Kim Il Sung, the grandfather of Kim Jong Un. They also came a day ahead of South Korean parliamentary elections.

In the South Korean elections, President Moon Jae-in's liberal ruling party, which espouses greater reconciliation with North Korea, is expected to defeat the main conservative opposition amid a slowdown in the number of new coronavirus infections in South Korea, according to pre-election surveys.

North Korea has repeatedly said there has been no coronavirus outbreak on its soil. But many foreign experts are skeptical of that claim and have warned that an outbreak in the North could become a humanitarian disaster because of the country's chronic lack of medical supplies and fragile health care infrastructure.