SEOUL, May 2 (Xinhua) -- South Korea's military on Monday expected the Democratic People's Republic of Korea (DPRK) to conduct another nuclear test in and around the country's ruling party convention scheduled for Friday.

Defense Ministry spokesman Moon Sang-Kyun told a press briefing that the DPRK will likely carry out additional nuclear test or launch additional missiles such as Musudan "by surprise" before or after the party congress in consideration of the DPRK's actions and will.

Pyongyang announced a plan last week to hold the seventh ruling Workers' Party of Korea (WPK) convention on May 6, the first since 1980.

Moon said the DPRK had launched ballistic missiles since top DPRK leader Kim Jong Un gave orders on March 15 to test a nuclear warhead and ballistic rockets capable of carrying the warhead "in a short time."

Ahead of the seventh WPK congress, the DPRK had test-fired several ballistic missiles to show its nuclear strike capability, the spokesman said.

In the past two weeks, the DPRK conducted the test-launch of three Musudan intermediate-range ballistic missiles, which South Korea's military saw as failures because the missiles exploded in mid-air or crashed in waters.

The DPRK announced a successful launch of a ballistic missile from a submarine on April 24, and South Korea's military said Pyongyang had partially advanced in its technology.

According to South Korea's military and intelligence assessments, Pyongyang has already completed preparations for the fifth nuclear test at a main nuclear test site in Punggye-ri in northeastern DPRK where the country conducted all of its four nuclear detonations. The latest test happened on Jan. 6.

Moon added that the DPRK completed preparations for the fifth nuclear test and can do it at any time.