South Korea on Friday launched its first military spy satellite, a little over a week after North Korea claimed to put its own spy satellite into orbit for the first time as tensions rise between the rivals.

Launched from California's Vandenberg Space Force Base using SpaceX's Falcon 9 rocket, it was the first of five spy satellites South Korea plans to send into space by 2025 under a contract with SpaceX. The event had been scheduled for earlier this week but was pushed back because of weather conditions.

South Korea has had no military reconnaissance satellites of its own in space and has partially resorted to US spy satellites to monitor moves by North Korea.

When operated together with South Korea's so-called three-axis system — preemptive strike, missile defence and retaliatory assets — experts say spy satellites will significantly boost the country's defence against North Korea.

After two launch failures earlier this year, North Korea said it successfully placed its “Malligyong-1” spy satellite into orbit last week. South Korea confirmed that the satellite entered orbit, but officials said they need more time to verify whether it is working properly.

North Korea said on Tuesday that leader Kim Jong Un reviewed imagery taken by the Malligyong-1 satellite of the White House and the Pentagon in Washington and US aircraft carriers at a navy base and a shipyard in Virginia.

North Korea earlier said the satellite also transmitted photos of US military facilities in Guam and Hawaii and key sites in South Korea.

North Korea hasn't yet released those photos. Outside experts remain sceptical about whether its satellite can send high-resolution imagery and perform proper military reconnaissance.

The North Korean satellite launch sparked immediate, strong condemnations from the US, South Korea and others. Multiple UN Security Council resolutions ban any satellite launches by North Korea, viewing them as covers for testing its long-range missile technology.

North Korea responded angrily, saying it has sovereign rights to launch spy satellites to cope with what it calls increasing US hostilities. It said it would also launch additional ones.

“The main threat to international peace and security does not come from the exercise of (North Korea's) sovereign right but from the US high-handed and arbitrary practices to disturb and oppress it,” Kim Yo Jong, the influential sister of North Korean leader Kim Jong Un, said in a statement on Thursday.

The satellite launches have inflamed animosities between the rival Koreas, and both nations have taken steps to breach a previous military agreement meant to ease frontline military tensions.

Spy satellites are among the high-tech weapons systems that Kim has publicly vowed to introduce. Since last year, North Korea has conducted about 100 ballistic missile tests, part of efforts to modernize its arsenal of weapons targeting South Korea and the United States.

In response, South Korea and the US have expanded their military training and enhanced “regular visibility” of US strategic assets, including aircraft carriers, nuclear-capable bombers and a nuclear-armed submarine in the Korean Peninsula.

South Korea's spy agency told lawmakers last week that Russia's technological assistance likely enabled North Korea to place its spy satellite into orbit. South Korea, the US and Japan have accused North Korea of seeking high-tech Russian technologies needed to enhance its military programs in return for supplying conventional arms to support Russia's war in Ukraine. Both Russia and North Korea have denied the allegations.