North Korea fired off what appeared to be a mid-range ballistic missile late Thursday, hours after it carried out a similar launch, but both attempts seem to have ended in failure, the South Korean military said.

North Korea launched an intermediate-range ballistic missile (IRBM), presumed to be a Musudan, at around 7:26 p.m. near its eastern city of Wonsan, according to Seoul's Joint Chiefs of Staff.

It said the missile probably blew up midflight.

The move came on the heels of the North launching the same type of missile at 6:40 a.m. Thursday. This missile is known to have crashed a few seconds into its flight.

The back-to-back launches on the same day marked the second and third times that Pyongyang has tested a Musudan, or BM-25, missile in less than two weeks.

North Korea made its first botched attempt to launch the Musudan missile on April 15, the birthday of North Korean founding father Kim Il-sung. The launch ended in what experts called a catastrophic failure, reportedly due to engine problems.

The North's three consecutive failed tests indicate the unreliability of the communist country's IRBM capability.

With a targeted range of 3,000-4,000 kilometers, the missiles are designed to reach as far as Guam, where a large number of United States military forces are stationed. Pyongyang presumably wants to arm these missiles with nuclear warheads that they may be developing.

North Korea is believed to have deployed some 50 Musudan missiles since 2007.

The North's missile tests came as the North's ruling Worker's Party of Korea (WPK) is preparing to hold its first party congress in more than three decades on May 6.

The party congress is widely expected to serve as a venue to help North Korean leader Kim Jong-un reaffirm his grip on power at a time when his country is struggling to tackle tougher U.N. sanctions.

The North's failed tests are likely to irritate the North's leader who has threatened to conduct a nuclear warhead explosion test and launch ballistic missiles "in a short time," analysts say.

They said that the failed launches may provide a greater incentive for North Korea to conduct a nuclear test ahead of the country's party congress in order to save face. (Yonhap)