SEOUL - South Korean President Park Geun-hye said Monday that it should be taken seriously for the Democratic People's Republic of Korea (DPRK) to have ratcheted up its aerial reconnaissance over South Korea's territorial air with drones.

"Drones suspected of coming from North Korea (DPRK) appeared to spy on all directions of our country, but our military has not recognized it at all. It represents problems in our air defense and ground reconnaissance systems," Park said during a meeting of senior presidential aides.

Park said the DRPK's stronger aerial reconnaissance along with its continued missile launches should be viewed as seriously, ordering officials to draw up countermeasures to block and repel any DPRK provocations.

Her comments came after three suspected DPRK drones were found in regions close to the western and eastern frontlines in the past two weeks.

One more unmanned aerial vehicle (UAV), possibly sent by the DPRK, was found Sunday in Samcheok, about 290 km east of Seoul and some 130 km south of the military demarcation line between the two Koreas.

It was similar, in size and shape, to the one discovered on March 24 in Paju, the northwestern South Korean city close to the land border. Both UAVs had triangular wings and a rectangular hole, within which a small camera was carried.

On March 31 when the two Koreas exchanged artillery fire, another UAV, which South Korea suspected of coming from the DPRK, was discovered on the Baengnyeong Island just south of the disputed western sea border.

The two UAVs, spotted on Baengnyeong Island and in Paju, carried cameras, which took aerial photos of military installations and even the presidential office Blue House.

Several DPRK UAVs reportedly flew over South Korea's airspace without being recognized. Some were detected by the naked eye in frontline areas, but they were depicted as birds on the radar screen for their small size.

Park said concerns became stronger among South Koreans due to DPRK provocations, including the recent series of missile launches, another nuclear test threats, the exchanging of artillery fires and the spy drone dispatches.

On March 30, the DPRK threatened a "new form" of nuclear test to bolster up its nuclear deterrence, raising fears over the fourth nuclear test following those in 2006, 2009 and 2013.