Four North Korean freighters steamed into this seaport early this morning and began unloading 25,000 tons of cement for the South Korean Red Cross.

North Korean officials wearing lapel buttons with pictures of their president, Kim Il Sung, watched from the decks as cranes lowered 110-lb. sacks onto piers in an isolated corner of the harbor.

North Koreans were last seen in Inchon, openly at least, in the spring of 1951, just before they abandoned the city in the face of an attack by U.S. forces during the first year of the Korean War.

Four other North Korean ships, also carrying cement, drew close today to another South Korean port, Pukpyong. Rice, cloth and medicine were delivered by truck for a second day at the Demilitarized Zone that separates North and South.

The South announced tonight that in return it was sending the North 800 special gift kits of consumer goods. Each included a digital watch, a tape cassette player and radio, stockings, women's underwear, material for traditional Korean women's attire, cooking herbs, cosmetics and shoes.

Each kit was worth about $750, according to the officials. They were being sent to the North aboard the last of approximately 750 trucks that brought North Korean goods to the Demilitarized Zone today. Each was intended as a gift for the North Koreans who took part in the delivery.

Compassion for flood victims in the South is the official explanation for the North's shipments. However, the two deeply mistrustful governments are using the forum to resume contact between their Red Cross societies that was broken off in 1977.

South Korean officials said today that the two sides were discussing a trip by North Korean Red Cross representatives to the South's capital, Seoul. That was not part of the original plan and could signify that dialogue will continue.

When the sun rose in Inchon today, the four North Korean vessels were tied up at the docks, having arrived during the early morning hours.

They were calling at a city that holds a special place in South Korea's military history. There Gen. Douglas MacArthur staged a surprise landing on Sept. 15, 1950, turning the tide in the North's three-month-old advance into the South.

Occupying North Koreans were quickly driven out but returned several months later with Chinese support and recaptured the city. They were driven out again in March 1951 by U.S. forces.

Some Inchon residents today gathered in a hilltop park that overlooks the harbor to catch a glimpse of the North Korean ships. Spectators were barred from the port area.

Officials of the two sides engaged in much handshaking and smiling. But workers from North and South generally ignored one another, talking only when the business at hand required it.

"My impression is that they are too hard and expressionless," said a South Korean truck driver as he watched the northerners from his cab. They were the first North Koreans he had ever seen, he said.

South Korean journalists standing on the pier shouted questions to the visitors ranging from wage rates in the North, to military service requirements and the 1988 Olympics. The games will be held in Seoul, a point of particular pride for the South Korean government.

Would the North send a team, one North Korean was asked. "Since many socialist countries believe Seoul is not the proper place for the Olympic Games," he replied, "we are studying the question."

One North Korean Red Cross official aboard the vessel Kumsusan complained that he had been asked repeatedly what he thought of Inchon, "I don't know," he said. "I haven't seen anything of the city."

South Korean media have played down the event. In this morning's newspapers in Seoul, the dedication of a new stadium for the 1988 Olympics got more prominent play than the first day of the deliveries.

North Korean officials declined an invitation from their southern counterparts to go to a hotel in Inchon for a rest. In general, the 365 or so North Koreans on the four ships left them only for specific purposes.

Economic development is a key element of the competition between North and South. The South Koreans may have seen the excursion into town as an opportunity to impress the visitors with the city's size and prosperity.

On the pier, South Korean officials inspected samples of cement and declared that their own cement was superior.

Four more North Korean ships are scheduled to enter Inchon Monday.