(CNN) -- Two drones, suspected of being from North Korea, have crashed in South Korea in the last two weeks, according to government officials from the South. The discoveries raise questions over South Korea's air defense and the North's aerial capabilities.
On Monday, a drone was discovered on Baengnyeong Island in the Yellow Sea, a strategically important location for the South's military. The drone crashed on the same day as the two Koreas exchanged fire off their western coasts.
South Korean government officials told CNN the most recent drone was traveling in a southward direction.
"We are investigating the drone that crashed into Baengnyeong Island with the assumption that it is North Korean," said a Blue House spokesperson.
Earlier, on March 24, another drone had been found in Paju, a city that sits a few miles south of the Demilitarized Zone. According to local media, the drone contained an image of the Blue House, the office and official residence of Park Geun-hye, the South Korean president.
The drone discovered in Paju had a North Korean-style word found on it, leading government officials to believe that both aircraft came from the country to undertake aerial surveillance.
The South Korean Ministry of National Defense said the small "elementary level" drones were fit with Japanese-made cameras and colored blue.
North Korea could be flying drones because it doesn't possess satellites to collect aerial information, said Professor Koh Yuwhan, a North Korean expert at Dongguk University in Seoul.
"The scary part of this is that the same drones can be used for terrorist attacks by loading weapons posing serious danger," he said. He added that another reason for Pyongyang sending the drones could be to show their capabilities.
North Korea has previously flaunted its drones during military parades.
An annual escalation?
North Korea's rhetoric has intensified in recent weeks.
South Korean and U.S. forces are currently conducting annual joint military drills, which North Korea typically denounces -- it recently accused the United States of "aggression and interference" through its state-run news agency, KCNA.
Last month, North Korea fired rockets from its eastern coast, drawing criticism from South Korea and its allies. North Korea called the actions "self-defense."
On Sunday, North Korea warned it was preparing to test another nuclear device, prompting fresh criticism from the United States.
"(We) would not rule out a new form of a nuclear test aimed at strengthening our nuclear deterrence," North Korea's Foreign Ministry said in a statement carried on KCNA. "The U.S. had better ponder over this and stop acting rashly."
The statement did not specify what the ministry meant by a "new form" of test.
On Monday, following the unusual step of informing its neighbors of live-fire drills, North Korea fired ordnance in and around the Northern Limit Line, the de facto maritime border between the two. Several North Korean shells landed in South Korean waters, prompting return fire.
Hundreds of shells were exchanged between the two forces, according to South Korea's semi-official news agency Yonhap. No injuries resulted from the incident.
The recent incident raised stern warnings from allies of both Korean nations.
China, North Korea's staunch ally, expressed concern over escalating tensions.
"China opposes actions that undermine (the) peace and stability of the Peninsula and urge all parties to keep calm, exercise restraint, be discreet in words and deeds," Hong Lei, China's foreign ministry spokesperson, said earlier this week.
U.S. Secretary of Defense Chuck Hagel echoed the sentiment. "The provocation that the North Koreans have, once again, engaged in, is dangerous and it needs to stop," he said.
Journalist Stella Kim and Paula Hancocks reported from Seoul, South Korea. Madison Park wrote from Hong Kong.