The firing of the short-range missile off North Korea's west coast came after South Korean President Lee Myung-bak's Sept. 26 meeting with security ministers and may have been related to that meeting, the government source told Yonhap.
Prior to that, Lee and his security officials had decided to warn the North against any provocation ahead of South Korea's presidential election set for December.
"The missile was estimated to have flown about 80-90 kilometers (49-56 miles)," the source said.
"The test-firing could be a part of the North's routine efforts to improve their capabilities and range, but there was an assessment that it could be a reaction to our government's movement," the source said.
The report said there have been numerous recent intrusions around the Yellow Sea border by North Korean fishing boats, and quoted analysts as saying through such violations as well as propaganda efforts, the North may be trying to promote social divisions in the South ahead of the December poll.