Image caption The Korean delegations met on Wednesday

North and South Korea have ended talks on reopening a jointly-run industrial zone in Kaesong without reaching a deal, South Korean officials say.

However, both sides have agreed to meet again on 15 July for more talks, said the South's chief delegate, Suh Ho.

Over the weekend, the two sides agreed in principle to restart operations at the industrial complex.

Work at Kaesong has been suspended since mid-April, when North Korea withdrew its workers.

The move came amid high tensions after Pyongyang's 12 February nuclear test.

The Kaesong complex, which is located just inside North Korea, is home to more than 120 South Korean factories which employ some 53,000 North Korean workers.

"Talks have been concluded without any agreement reached," a spokesman for South Korea's Unification Ministry told Yonhap news agency.

The spokesman said the two sides repeatedly met during the day but were unable to resolve their differences.

"We both agreed that the complex should be maintained and further developed," Mr Suh told reporters after the two countries met on Wednesday.

The joint project is both a symbol of inter-Korean co-operation and a key source of revenue for Pyongyang.

Kaesong Industrial Zone Launched in 2003, largely financed by the South to increase co-operation

More than 120 factories employ North Koreans in manufacturing industries, with goods exported to the South

Complex as a whole produced $470m worth of goods in 2012 - the biggest contributor to inter-Korean trade

South Korean companies pay more than $80m a year in wages to North Korean workers Q&A: Kaesong Industrial Complex

'Big differences'

On Tuesday, a small team of South Koreans crossed into North Korea to check communication and power lines. It was the first time South Koreans had entered the zone in two months.

On Wednesday, around 100 delegates, including dozens of government officials and businessmen and engineers, entered North Korea to begin formal talks.

The visit is the first positive sign of thawing relations between the two Koreas in more than three months, but there are still big differences to bridge, the BBC's Lucy Williamson in Seoul reports.

Both sides blame the other for the suspension of operations at Kaesong, and South Korea is now demanding safeguards as a condition for reopening the zone, our correspondent adds.

Last week, some South Korean firms threatened to abandon the zone entirely and relocate their equipment.