The bodies of four Palestinian workers were recovered on Sunday from a collapsed tunnel on border between the blockaded Gaza Strip and Egypt, according to a Palestinian security source.

The four men aged 22 to 45 "were found dead after the tunnel they were working in was flooded nine days ago by the Egyptian army," local authorities in the Gazan city of Rafah near Egypt's border said in a statement.

The workers had gone missing when a cross-border tunnel collapsed a week ago, the source told Anadolu Agency, requesting anonymity because he was unauthorized to speak to media.

In recent months, the Egyptian army has been flooding a network of cross-border tunnels linking Egypt's Sinai Peninsula to the Gaza Strip with seawater.

Subject to a years-long blockade by Israel, the Gaza Strip, which is ruled by Palestinian movement Hamas, had come to depend on the tunnel network to import desperately-needed commodities, including food, fuel and medicine.

Since the 2013 military coup against President Mohamed Morsi, Egyptian authorities have cracked down on the tunnels along border with the Palestinian territory.

On Saturday, the Egyptian army said its forces had destroyed seven cross-border tunnels on Gaza border last month.

In 2014, Egyptian authorities began to establish a buffer zone in North Sinai's city of Rafah along Gaza border following a spate of militant attacks against army and police forces.

In recent months, at least 20 Gazans have died in both militant and smuggling tunnels in the strip of some 2 million people.