South Korea and the United States are reported to have raised their joint military surveillance level, amid indications that rival North Korea could be preparing for a missile test.
South Korean and U.S. officials were quoted as saying North Korea may have readied at least two medium-range missiles for launch from its east coast.
South Korean Foreign Minister Yun Byung-se told lawmakers on April 10 that the launch could happen "at any time."
"Probably [North Korea would launch] a new type of missile, called Musudan, which is a mid-range missile," he said. "Its range is about 3,500 kilometers. It depends on North Korea's decision how far they will send it. It can fly to short distance or to longer distance just like they did in the past flying over Japan."
South Korea’s Yonhap news agency, quoting an unnamed military official, said the South Korea-U.S. Combined Forces Command had raised its "Watchcon" status to reflect a potential "vital threat."
After the UN Security Council tightened sanctions on North Korea following its third nuclear test in February, Pyongyang has issued a series of threats.
North Korea has also been angered by ongoing U.S.-South Korean military exercises.
On April 9, the communist government warned foreigners to evacuate from South Korea, citing the threat of war.
Last week, North Korea suggested foreign embassies in its capital be evacuated by April 10.
In Tokyo on April 10, Japanese Defense Minister Itsunori Onodera inspected missile defense batteries deployed in the center of the city following the North Korean threats.
He spoke to one of the soldiers manning a Patriot missile launcher outside the Defense Ministry and told him "at this uncertain time [to] be ever ready to leap into action whenever the order may come."
The United Nations' Secretary-General Ban Ki-Moon has warned that a small incident could provoke an "uncontrollable" situation on the Korean peninsula.
North Korea observes several key anniversaries in the next few days that could be a pretext for a military show of strength.
Seoul Says Pyongyang Behind Computer Attacks
Meanwhile, in related news, South Korean officials say an initial investigation has found that North Korea's military intelligence agency was behind a major cyberattack on South Korean broadcasters and banks last month.
A spokesman for the Korea Internet Security Agency (KISA) told reporters on April 9 that investigators had found that six computers in North Korea were used to access South Korean servers using more than 1,000 IP addresses overseas.
He said the attack was similar to past North Korean hacking and had been prepared for at least eight months.
The March 10 attack completely shut down the computer networks of three South Korean TV broadcasters and halted financial services at several banks.
With reporting by Reuters, AP, and AFP