The Korean Air received a letter threatening bomb attacks against its flight flying between Thailand and South Korea, newspaper The Nation reported on Monday.

The threat letter mailed from Bangkok was sent to Korean Air's office at Bangkok International Airport on Friday.

"We have no idea who sent the unsigned letter, which was typed in English," an unnamed official of the airline was quoted as saying.

He also said that security checks on passengers boarding all Korean Air flights in Bangkok had been intensified and so far there's no cancellation of flight after the bomb threat.

Korean Air services the Bangkok-Seoul route twice a day, seven days a week.

South Korean embassy in Bangkok on Wednesday received a letter made by an unknown "Yellow-Red Overseas Organization" threatening terrorist attacks against South Korean target for the government allied with the United States in the Iraq war.

The group also sent a letter to the Pakistani embassy to Bangkok and threatened attacks on airlines and other major facilities of Australia, Japan, Kuwait, Pakistan, the Philippines,Singapore, South Korea and Thailand, here and overseas, between April 20 and 30.

Police have taken the threat seriously and reinforced security guard around the South Korean and Pakistani embassies.

The Korean Air official also reportedly said that aviation industry sources told him offices of three other airlines in Bangkok had received similar threats in the past week.

The Bangkok International Airport source said the authorities were aware of the threat but had no immediate plan to intensify security, which was already "tight", according to The Nation.

Meanwhile, the police didn't rule out the possibility that the threat was just a prank.

The Thai embassy to Sweden in earlier April received a letter threatening attack against Thailand if the Thai troops didn't immediately withdraw from Iraq.

The security issue has become a major concern of the Thai government since the country was believed to have more involved with the United States' anti-terrorism war in last year and the southern provinces were caught in unrest in this year.

Thailand was granted with the Non-NATO status last October for arresting Jemaah Islamiyah's (JI) second headsman Hambali in August and sending 400-odd troops to Iraq in September.

Source: Xinhua