The objects traveled off the peninsula's east coast and the South Korean military is analyzing the situation, an official from the South Korean Defense Ministry said.
The news came one day after the United Nations Security Council voted
to impose a broad array of sanctions against North Korea because of that nation's recent nuclear test and missile launch -- both of which defied current international sanctions.
The U.N. resolution
that brought about the sanctions aims to cripple the economic factors that fuel North Korea's nuclear and ballistic missile programs.
According to Samantha Power, the U.S. ambassador to the United Nations, the sanctions will:
-- Require that all North Korean planes and ships carrying cargo be inspected. Previously, nations only inspected planes and ships when they had "reasonable grounds."
-- Ban Pyongyang from exporting most of the country's natural resources.
-- Prohibit nations from providing training to North Korean nationals in fields that could advance the nation's missile and nuclear programs.
-- Ban member states from allowing North Korea to charter foreign vessels or aircraft and ban all nations from operating any vessels that use North Korean flags.
-- Prohibit the supply of aviation fuel, including rocket fuel, and the sale of small arms to North Korea.
Discussions about new sanctions started after North Korea claimed to have successfully tested a hydrogen bomb in January
-- its fourth nuclear test.
The nuclear test and missile launch outraged the Security Council and worried neighboring nations.
South Korean President Park Geun-hye released a statement Thursday about the new sanctions, thanking the international community for its efforts.
"I sincerely hope that the North will abandon its nuclear development program and embark on a path of change, and I will make further efforts for peace and unification of the Korean Peninsula," the President said.
Japan's chief cabinet secretary said Thursday his government does not believe there is a threat to Japanese security in relation to the incident.
And China called for calm.
"The current situation on the Korean peninsula is complicated and sensitive," Chinese Foreign Ministry spokesman Hong Lei said Thursday. "We hope the relevant parties can keep cool heads and not take any actions that will escalate tensions."