The failed launch from the east coast came a day after North Korea held a military parade in its capital, marking the birth anniversary of the state founder, Kim Il Sung, in which what appeared to be new long-range ballistic missiles were on display.
Pence is due in Seoul at the start of a 10-day trip to Asia in what his aides said was a sign of the US commitment to its ally in the face of rising tension over North Korea.
A US nuclear-powered aircraft carrier strike group is also heading for the region.
The North has warned of a nuclear strike against the United States if provoked. It has said it has developed and would launch a missile that can strike the mainland United States but officials and experts believe it is some time away from mastering the necessary technology.
"The North attempted to launch an unidentified missile from near the Sinpo region this morning but it is suspected to have failed," the South's Office of the Joint Chiefs of Staff said in a statement.
The US Pacific Command said the missile "blew up almost immediately", adding the type of missile was being analysed.
Pence had been briefed on the failed launch en route to Seoul and had been in touch with Trump, the White House said.
South Korea's Yonhap news agency cited an unnamed South Korean intelligence source as saying the missile appeared to have not flown far from its land-based launch site.
The North launched a ballistic missile from the same region earlier this month ahead of a summit between the leaders of the United States and China, its key ally, to discuss the North's arms programme.
That missile flew about 60km but what US officials said appeared to be a liquid-fuelled, extended-range Scud missile only travelled a fraction of its range before spinning out of control.
A US Navy attack on a Syrian airfield this month with Tomahawk missiles raised questions about US President Donald Trump's plans for reclusive North Korea, which has conducted several missile and nuclear tests in defiance of United Nations sanctions, regularly threatening to destroy the United States.
Sinpo, where the launch took place, is the site of a North Korean submarine base and where the North has tested the submarine-launched ballistic missile (SLBM) it is developing.
“It appears today’s launch was already scheduled for re-launching after the earlier test-firing” Kim Dong-yub, a military expert at Kyungnam University's Institute of Far Eastern Studies in Seoul.
“This launch can possibly be a test for a new type of missile or an upgrade,” Kim added.
Tension had escalated sharply in the region amid concerns that the North may conduct a sixth nuclear test or a ballistic missile test launch around the April 15 anniversary it calls the "Day of the Sun."
The White House has said Trump has put the North "on notice" while the possibility of US military action against Pyongyang has gained traction following US strikes against Syria on April 7.
Impoverished North Korea and the rich, democratic South are technically still at war because their 1950-53 conflict ended in a truce, not a peace treaty. The North regularly threatens to destroy the South and the South's main ally, the United States.
