A South Korean presidential spokesman said Wednesday an inter-Korean military hotline was still open after North Korea reportedly severed another hotline with Seoul earlier amid its escalating war rhetoric.

"The military communication is working normally and we will seek to convey any message to the North via the channel when necessary," AFP quoted the spokeswoman as saying.

South Korea's unification ministry confirmed Monday North Korea had severed a communication hotline between the two Koreas, which do not have diplomatic relations.

Pyongyang cut the hotline to protest an ongoing US-South Korea joint military drill held amid rising tensions on the Korean Peninsula.

A spokesman for the North Korean Ministry of the People's Armed Forces on Wednesday again threatened to launch a preemptive nuclear strike if the US "dared to ignite the fuse of a nuclear war," Pyongyang's official KCNA news agency reported.

The ministry also confirmed that Pyongyang had scrapped the 60-year-old Korean War Armistice Agreement.

Meanwhile, South Korea's Yonhap news agency quoted a military source as saying Wednesday that North Korean fighter jets had increased training flights in recent days.

If neither side on the Korean Peninsula takes action to cool tension, the situation could spiral out of control and a small-scale conflict could possibly break out, Cui Zhiying, director of the Korean Peninsula Research Center at Shanghai-based Tongji University, told the Global Times.

"But a large-scale war is unlikely at the moment as this is not what the relevant parties want to see," he added.

"South Korea is not a signatory to the Korean War Armistice Agreement, but the US is. Most of Pyongyang's threats target Washington," noted Lü Chao, director of the Korean Research Center at the Liaoning Academy of Social Sciences.

"North Korea wants to use such threats to deflect US-led international pressure over its nuclear test," he said.

Agencies contributed to this story