Seoul, South Korea - North Korea fired at least 10 missiles Wednesday, including at least three toward South Korean territory, triggering alerts on televisions throughout the country and air raid sirens in an island province off the coast.

South Korea's military says one of the missiles fell into waters just 57 kilometers east of Sokcho, a coastal tourist city in South Korea's northeast. Another missile landed 167 kilometers from Ulleung County, a sparsely populated island region off South Korea's east coast. The third fell in international waters just 26 kilometers south of the de facto inter-Korean sea border, officials said.

North Korea has fired about 50 ballistic missiles this year - a record high - but until today none had been launched toward South Korean territory and none had resulted in public air raid alerts.

The developments further raise tensions on the Korean Peninsula, where both sides have increased displays of military strength.

'The launch is very unusual and unacceptable as it fell close to our territorial waters in the NLL for the first time since the division' of the Korean Peninsula, said Shin Chul Kang, Lieutenant General of South Korea's Army.

'Our military will respond decisively,' Shin added.

South Korean President Yoon Suk Yeol ordered 'strict measures be taken swiftly to ensure North Korea pays a clear price for its provocation,' according to a statement from his office.

At a background briefing, a South Korean military official said North Korea launched over 10 missiles of various types on both sides of the Korean Peninsula.

On Ulleung Island, loud sirens sounded for about 2-3 minutes early Wednesday, but residents did not know it was an air raid warning, reported South Korea's JTBC broadcaster. On televisions throughout the country, some broadcasts were interrupted at 8:55 a.m. to alert residents about the launches.

Such alerts are highly unusual in South Korea, where North Korean missile launches are hardly mentioned in newscasts.

The launches come as South Korea mourns the deaths of at least 156 mostly young people who were crushed to death Saturday in a crowd surge during Halloween celebrations.

There are also concerns of a North Korean nuclear test and as Pyongyang issues increasingly firmly worded warnings toward the United States and its ally South Korea.

On Tuesday, North Korea warned for a second consecutive day that Washington and Seoul should halt military exercises, which have recently been increased as a response to North Korea's moves.

'Such military rashness and provocation can be no longer tolerated,' said Pak Jong Chon, secretary of the Central Committee of North Korea's Workers' Party, in a statement posted to North Korean state media.

A day earlier, a North Korean foreign ministry official warned of 'powerful follow-up measures' if the U.S.-South Korean drills do not stop.

South Korean and U.S. officials have for months warned that North Korea is in the final stages of preparations for what would be its seventh nuclear test since 2006.

On Tuesday, U.S. State Department spokesperson Ned Price dismissed North Korea's latest threats and repeated Washington's long-time insistence that the joint military exercises were defensive in nature.

'Unfortunately, this seems to be the DPRK reaching for another pretext for provocations it has already undertaken, potentially for provocations that it might be planning to take in the coming days or coming weeks,' Price said.

Lee Juhyun contributed to this report.