Four Belgians held hostage in the Middle East since they were seized in November 1987 by a radical Palestinian group were freed Saturday and were due back in Belgium during the night, the foreign ministry said.

In exchange, a Palestinian held in Belgium jails since a July 1980 hand grenade attack on a group of Jewish children in Antwerp was freed by Belgian authorities. One Jewish boy was killed and nearly 20 were wounded in the attack.Officials declined to say where the exchange took place. The deal had been under negotiation for months.

The Beirut-based Fatah-Revolutionary Council, the terrorist group of Abu Nidal, said earlier in the week that on the request of the Libyan leader, Col. Moammar Gadhafi, it would free the four Belgian hostages, who were seized from the pleasure boat "Silco" in the eastern Mediterranean.

The spokesman, Walid Khaled, was not available for comment Saturday on the Belgian government's announcement.

The Belgians freed were Emmanuel Houtekins, 45; his wife, Godelieve Kets, 51, and their two children, Laurent, 20, and Valerie, 19.

"I am extremely happy to be able to announce that after so many years of separation and several uncertain months, they are in an airplane and will land in Belgium tonight," said Belgian Foreign Minister Mark Eyskens. "Their state of health is excellent."

Eyskens telephoned family members in Belgium Saturday to inform them of their relatives' freedom. The sister of Godelieve Kets spoke of her "joy to learn of the freedom of my sister," but a reunion was not likely until sometime on Sunday.

Belgian officials refused to say where the Palestinian freed from a Belgian jail was taken to, but confirmed he had left Belgium.

Said Nasser, convicted in the 1980 hand-grenade attack, was imprisoned at a jail in Louvain, near Brussels. Under Belgian law, a prisoner serving a life term can win release after 10 years for good behavior.

Four others also seized from the "Silco" had previously been released.