SEOUL (Reuters) - North Korea's defence ministry blamed South Korea's military for sending drones into its territory for political purposes, calling it an infringement upon the country's sovereignty, state media KCNA said on Monday.

The ministry announced final results of its investigation after claiming that South Korean drones flew over Pyongyang at least three times this month to distribute anti-North leaflets. KCNA has also published photos of what it described as a crashed South Korean military drone.

During an analysis of the drone's flight control programme, North Korean authorities said they uncovered more than 230 flight plans and flight logs since June 2023, including a plan to scatter "political motivational rubbish."

An Oct. 8 record showed that the drone had departed the South's border island of Baengnyeongdo late at night and released leaflets over the foreign and defence ministry buildings in Pyongyang a few hours later.

Seoul's defence ministry did not immediately have comment but has said Pyongyang's unilateral claims were "not worth verifying or a response."

A North Korean spokesperson warned that the country would respond with "merciless offensive" if such a case recurs, KCNA said.

Tensions between the Koreas have rekindled since the North began flying balloons carrying trash into the South in late May, prompting the South to restart loudspeaker propaganda broadcasts.

Seoul and Washington have said North Korea has sent 3,000 troops to Russia for possible deployment in Ukraine, which could mean a significant escalation in their conflict. Pyongyang said on Friday that any move to send its troops to support Russia would be in line with international law.

(Reporting by Hyonhee Shin; Editing by Lisa Shumaker)