North Korea test-fired a pair of short-range missiles into its eastern waters this past week in a likely response to ongoing routine U.S.-South Korean military drills, a South Korean official said Saturday.

The North launched what appeared to be KN-02 missiles during its own drills, the military official said. He would not say on which day the missiles were fired or give other details, and declined to be named, citing policy.

North Korea routinely launches short-range missiles in an effort to improve its arsenal, but the latest test comes at a time of rising tensions. Pyongyang has threatened nuclear strikes on Seoul and Washington because of the U.S.-South Korean drills and recent UN sanctions over its third nuclear test.

Analysts say Pyongyang's threats are partly an attempt to push Washington to agree to disarmament-for-aid talks.

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South Korean Marines patrol on Yeonpyeong Island, South Korea earlier in March. (Yonhap, Yun Tae-hyun/Associated Press)

North Korea threatened a pre-emptive nuclear strike against the United States last week in response to tough new UN sanctions it now faces for its latest nuclear test.

In a separate development, a dispute between the two halves of the Korean Peninsula over a group of South Korean-held islands appears to be heating up once more, with a new threat from a North Korean website.

The Uriminzokkiri website has warned the dispute could escalate to include another attack Yeonpyeong island, which the North shelled in 2010, killing four people and injuring 19.

"Even an accidental spark by the belligerents in their war games can grow into a fire, and the damage for those living along the border and on the five western islands will be great," the website said Friday after South Korean Prime Minister Chung Hong-won visited Yeonpyeong.