Seoul - Pyongyang on Tuesday reopened its border to hundreds of South Koreans stranded at a joint industrial complex, one day after it cut inter-Korean communications amid rising tension over US and South Korean military exercises.

Border traffic to and from the Kaesong industrial park in North Korea returned to normal, South Korean Defence Ministry spokesman was quoted as saying by the official Yonhap news agency.

More than 600 South Koreans were stranded after the North severed a military hotline in protest against the annual military exercises, accusing Seoul of threatening war.

The communist state put its troops on combat alert on Monday, the start of the 12-day manoeuvres.

The North Korean Peoples' Army informed South Korea in a hand-delivered letter that the border was reopened, but until communication was restored, visits had to be notified by that means, Yonhap said.

The Kaesong industrial complex is a major earner of foreign currency for the impoverished, highly militarized Stalinist state. More than 38,000 North Koreans work at Kaesong for about 90 South Korean companies, producing kitchen appliances, clocks or clothing.

In December, Pyongyang closed down its only train link to the South and limited border traffic to Kaesong as the communist leadership accuses Seoul of pursuing a confrontational policy since a conservative government took power in South Korea in February 2008. (dpa)