The US sent two nuclear-capable bombers on a 10,500km round trip to South Korea on Thursday in response to North Korean predictions of war, as one of the last inter-Korean telecoms links was shut down.

The two B-2 aircraft flew from Missouri and dropped dummy bombs on a training range on an island off the South Korean west coast, in a signal of Washington’s commitment to “deterring aggression”, according to a military spokesman.

The announcement demonstrates the US’s ability to target North Korea directly from its mainland bases, and follows two separate sorties over South Korea by US B-52 bombers in the past 10 days.

Tensions on the Korean Peninsula have been high after North Korea’s nuclear test in February and the consequent tightening of UN sanctions, and have been further fuelled as Pyongyang responds defiantly to joint exercises being carried out by US and South Korean forces.

North Korea’s state media agency, KCNA, continued the pattern of recent weeks by issuing several graphic threats on Thursday, warning that “the US nuclear threats and blackmail are turning into a reality”, and that Pyongyang would respond to a nuclear attack in kind. It condemned both a military co-operation deal agreed last week by the US and South Korea, and their annual joint exercises which continue until April 30.

“Discerning bluster from actual North Korean intent is always difficult, but recent actions suggest greater potential for another attack on South Korean military and civilian targets,” said Bruce Klingner, an analyst at the Heritage Foundation. He cited “very specific” threats against South Korean military units based on islands off the west coast of the peninsula – one of which was the target of a North Korean artillery attack which killed four people in 2010.