SEOUL, November 18 (RIA Novosti) - Seoul is still continuing to cooperate with authorities in North Korea's capital despite recent frosty relations between the South and the North, Seoul's assistant mayor said on Tuesday.

Relations between the two Koreas, which have not signed a peace treaty since the 1950-1953 war, worsened after recent protests by anti-Pyongyang organizations in Seoul that released balloons with propaganda leaflets over the demilitarized zone to the communist state in breach of bilateral agreements.

"Contacts continue, though they represent unilateral aid - not only to Pyongyang but also to other North Korean cities - rather than equal cooperation," Sang Bum Kim told Russian journalists.

The assistant mayor said that almost all major South Korean cities are involved in assisting North Korea, adding that the Gyeonggi-do Province in the country's northwest had offered its "highly developed experience in the agriculture sector."

The North Korean government said last week that it would close its land border with the South, citing Seoul's confrontational attitude and failure to honor bilateral agreements.

In response to Pyongyang's statement on the border closure, South Korea's Unification Ministry warned that it could harm bilateral relations.

The move comes amid increasing speculation over the health of North Korean President Kim Jong-il. Reports say he may have suffered at least one stroke. North Korea has denied this.

After coming to power in February, South Korean President Lee Myung-bak said he would review agreements reached at the 2000 and 2007 inter-Korean summits, and demand more in return from the North for the economic support provided by Seoul.