Despite returning 15 fishing boats confiscated from fisherman who traveled past limit, Gaza complains Israel should return more.

Israel has returned 15 fishing boats seized in recent years off the Gaza coast, the Israel Defense Forces said late Wednesday.

"The naval branch (navy) returned to Gaza 15 fishing boats which deviated from the Strip's permitted fishing zone and were seized over the years," the IDF statement read.

The small vessels were dragged back to shore by a boat from the Gaza fishermen's union, an AFP photographer said.

Because of security concerns, Israel bans fishing off the coast of Gaza beyond six nautical miles. Boats that exceed that limit are often fired on as a warning.

Gazan fisherman, meanwhile, were less than grateful for the return of the 15 boats, immediately demanding that Israel hand back the so-called dozens more vessels still in its possession.

"It is true this is the first time Israel has returned fishing boats... but its forces fire at fishermen before they've even exceeded the imposed limit, especially off southern Gaza," fishing union chief Nizar Ayyash claimed to AFP.

"There are still 60 boats held by the Israeli navy, and we demand Israel return them," he added.

Earlier on Wednesday, Israel allowed 14,000 tons of building material into Gaza - the largest single shipment since last summer's war with Hamas - despite the fact that Hamas is using such materials to rapidly rebuild its terror tunnels to attack Israel.