In a sign of more animosity to come, South and North Korea traded retaliatory measures on Wednesday with Seoul halting aid and Pyongyang nixing future family reunions, as tension soars on the peninsula after a deadly artillery attack from the communist state.

   Tuesday's assault on the small western South Korean island of Yeonpyeong left at least two marines and two civilians dead in one of the most violent armed clashes between the two countries since the 1950-53 Korean War ended in a truce.

   Hours after the crisis erupted, South Korea banned its nationals from traveling to North Korea and indefinitely postponed Red Cross talks scheduled for Thursday. On Wednesday, Unification Ministry spokesman Chun Hae-sung said Seoul was suspending the shipment of the remainder of flood aid that it had promised to the North.

   Denouncing Seoul for postponing Red Cross talks, the North said it no longer wants to conduct humanitarian projects with the South, including the reunions of families split by war.

   "As the South's Red Cross has declared the indefinite postponement of talks, we no longer seek to resolve humanitarian issues," the North Korean Red Cross said in a statement carried by the country's official Korean Central News Agency. "The South's Red Cross should bear the entire responsibility for ruining humanitarian programs, including family reunions."

   The North also said that the South should be held responsible for "driving circumstances to the state of war."

   In their previous round of Red Cross talks, the North had demanded 500,000 tons of rice and 300,000 tons of fertilizer in return for an agreement to hold family reunions more frequently.

   The impoverished country has received a total of 5,000 tons of rice, 3 million packs of instant noodles and 3,000 tons of cement in flood aid from the South since September.

   The remaining 7,000 tons of cement to be shipped to the North have been stopped from being delivered to the North Korean town of Sinuiju near the border with China, Chun said, adding that medical supplies worth 580 million won (US$500,000) were also halted.

   In what appeared to be a desperate attempt to keep alive sources of income for Pyongyang, the North's Web site, Uriminzokkiri, demanded Wednesday that the two Koreas hold talks to resume suspended cross-border tours to the Mount Kumgang resort in the North.

   The site did not make any mention of the artillery attack that prompted the South to return fire. Condemning the North, South Korea and the United States agreed Wednesday to hold a joint naval exercise mobilizing an aircraft carrier starting this weekend.

   The two Koreas held their last round of family reunions at the Mount Kumgang resort from late last month to early this month, a rare moment of peace between the countries whose relations have been tense for the past three years.

   The ties deteriorated to the worst level in years after the South blamed the North for the sinking of its warship. The North denies any role in the sinking that killed 46 sailors.

   The Unification Ministry said the ban on trips to North Korea will be extended for another day, citing concerns over the safety of its nationals in North Korea.

   About 760 South Koreans were staying in Kaesong and 14 others at the Mount Kumgang resort as of Wednesday, according to the ministry.

   The ban applies to South Koreans who regularly travel to Kaesong, but it essentially restricts all cross-border trips because Kaesong is the only place South Koreans routinely visit. (Yonhap News)