TAIPEI/SEOUL (REUTERS) - Taiwan's government became the first to urge its citizens to delay visiting South Korea amid rising tensions with the North after Pyongyang this week warned foreigners to leave or risk being caught in a"thermonuclear" war.

Despite the tide of invective from North Korea, tourist and business arrivals in South Korea appear to be rising, based on March data and projections for April from the Seoul government.

Taipei's foreign ministry issued a statement late on Wednesday asking Taiwanese to delay their trips for business, holidays and education. Its representative office in South Korea has set up a team to handle any emergency that might develop.

"It's a reminder to our people that the situation in Korea is unclear," spokesman Anna Kao said. "Our representative offices there are watching closely for any latest development."

People in Taiwan seemed unaffected by the tensions in Korea.

At noon, Taiwan's stock market had jumped 1.1 per cent, outperforming bourses in Seoul and China.

Taiwan lived for decades under threat of attack or invasion from China, which claims the self-ruled island as its own, although relations have improved dramatically in recent years.

Taipei's warning came as South Korea and the United States raised their military readiness after North Korea moved medium-range missiles to its eastern coast in an apparent preparation for a launch.

Government data from South Korea showed that foreign arrivals were up 11.9 per cent in March compared with the same period last year as visitors from China, Pyongyang's last major ally, jumped 57 per cent and arrivals from Europe and the United States rose by more than 10 per cent.

Tourist arrivals from Taiwan were up by 17 per cent.

"The numbers show that, like local residents, foreigners are not worrying about a war breaking out," said Lee Young Geun, an official at the Korea Tourism Organisation.

Top-end hotels in Seoul, which lies 50km from the heavily fortified border with North Korea, said room occupancy rates were steady. These include the Millennium Seoul Hilton, Westin Chosun and the Plaza Hotel.

However, that could change if the North moved beyond rhetoric and launched a missile.

The US and South Korean armed forces say their intelligence shows the North is ready for a launch, with speculation over a launch date tied to celebrations on April 15 to mark the birth of North Korea's founder Kim Il Sung.

"This is a critical week that will tell whether the tourism flows continue," said Plaza Hotel spokesman Kim Na Hye.

Tourists also appear to be willing to get as close to the North as they can at the heavily fortified Demilitarised Zone (DMZ) that separates the two Koreas.

Mr Brandon Noh, manager of the Koridoor travel agency, which organises trips to the DMZ, said it was business as usual, but said many people were calling to check that tours were still on.

At least one other tourist said fears were being magnified outside South Korea.

"Some of my friends were suggesting that I cancel my trip, but I said no, because I hadn't seen my son and grandchildren in over a year," said Marietta Mutter, who had flown from Texas to visit family in Seoul.