Egypt is building an anchorage for patrol boats on its Gaza sea border, further bolstering its defences against suspected weapons smuggling by Palestinians, security sources said.

One of the sources said the anchorage at Rafah, a town that straddles Gaza Strip and Egypt would be 10 metres deep and 25 metres long. Egypt is already constructing an underground barrier to cut off smuggling through tunnels in the area.

"The new anchorage will enhance the work of the Egyptian patrol boats on the sea border with Gaza and prevent any attempts of smuggling by sea," another security source in North Sinai told Reuters.

The first source said the anchorage was to ensure Palestinian fishing boats, which they suspect of carrying out the smuggling operations, do not come near Egypt's or Israel's coasts.

"It is to secure the area. It will be used to direct fishing boats in the area to ensure they do not cross the Israeli sea border and risk getting fired at," he told Reuters.

Large blocks have been moved to border post 1, the start of Egypt's border with Gaza, where the anchorage will be built.

Israel and Egypt maintain a blockade on Gaza, which is ruled by Hamas Islamists. Israel controls the air space, sea access and most of the entry points into the coastal enclave. Egypt controls the Rafah border.

Hamas official Sami Abu Zuhri condemned the Egyptian building work as a "clear plan to cement the blockade and the siege on Gaza".

In 2007, after Hamas gained control of Gaza, 30 Palestinian fighters arrived in Egypt in boats, all carrying weapons.

Egypt only confirmed last month it was building a steel underground barrier and has played down the scope of the dig on the 14 km frontier, although its foreign minister said this week it had been planned for a year.

Egypt is also building more watch towers along the border with Gaza to boost sea surveillance, security sources said.

On Thursday, three military personnel from the US embassy in Cairo visited Rafah to follow up on the building of the barrier, security sources in Rafah said, adding such visits had been taking place monthly.-Reuters