Relatives of two U.S. journalists sentenced to 12 years hard labor in North Korea called on the reclusive state to show compassion, while U.S. President Barack Obama's spokesman said the two were innocent and should be freed, Reuters reported.
Monday's harsh sentence by one of the North's top courts deepened the chill between Washington and comes as global powers are looking to punish destitute Pyongyang for a nuclear test in May that put it closer to having a working atomic bomb.
Analysts said Pyongyang is using the journalists as bargaining chips to gain the upper hand with Washington, which for years has tried to use sweeteners in return for Pyongyang reducing the security threat it poses to the North Asia region, responsible for one-sixth of the world's economy.
"We believe that the three months they have already spent under arrest with little communication with their families is long enough," the families for Laura Ling and Euna Lee, of U.S. media outlet Current TV, said on a statement obtained on Tuesday.
The two were arrested in March near the border between North Korea and China while working on a story for the company, co-founded by former U.S. Vice President Al Gore. The North convicted them of "grave crimes," saying they illegally entered the country.
"We ask the government of North Korea to show compassion and grant Laura and Euna clemency and allow them to return home to their families," they said.
The communist North maintains a network of prisons where inmates are overworked and underfed and brutality is the norm, human rights groups and defectors have said.
In Washington, White House spokesman Robert Gibbs said the journalists' fate should not be linked to the dispute over Pyongyang's nuclear program.
"If they (North Korea's leaders) wanted them for any other purposes, they would have made a big deal of it in domestic media," said B.R. Myers, an expert on the North's state ideology at Dongseo University in South Korea.
"The fact that they have not gives me hope that a resolution can be reached."
South Korea's main stock index dipped late on Monday as the news of the sentencing weighed on sentiment. Analysts say it would take a military clash at sea or on the border to have a major impact on global markets.
North Korea appears ready to further ratchet up tension by preparing for tests a long-range missile that could reach U.S. territory and mid-range missiles capable of striking anywhere in South Korea and in most of Japan, officials have said.
The North also issued a no-sail warning through the end of this month for a wide area off its east coast, indicating possible short-range missile tests. It launched a short-range missile in the area in May and a barrage of short-range missiles in 2006.
Analysts said the military grandstanding may be primarily aimed at the internal audience to help leader Kim Jong-il, 67, arrange for eventual succession in Asia's only communist dynasty for his youngest son, Swiss-educated Jong-un.
The U.N. Security Council may adopt a new resolution as early as this week to clamp down on the country's arms trade and finances, but members are divided on how to respond.
China, the North's biggest benefactor, is seen as nervous of measures that might push its fragile neighbor into collapse -- especially at a time when there is uncertainty about the health of leader Kim, who is believed to have suffered a stroke last year.
"China will support strong sanctions, but not extreme ones," said Qin Yaqing, Vice President of China Foreign Affairs University in Beijing and an adviser to senior leaders on regional affairs, in an interview with Reuters.
"We don't want sanctions that could further risk turmoil or serious instability in North Korea. That's in nobody's interests.
North Korea threatened on Monday to retaliate with "extreme" measures if the United Nations punished it for the nuclear test.
"Nobody can exclude the possibility that North Korea will opt for more missile launches or nuclear tests," Qin said.