Israel is using claims of tunnels under Egypt's border with Gaza as cover for its offensive against Hamas, the state-linked Al-Qahera News reported on Wednesday, citing a "high-level Egyptian source".

"There are no communications with the Israeli side regarding the allegations of the existence of tunnels on the border of the Gaza Strip and Egypt," the source told Al-Qahera, which is linked to state intelligence.

"Israel is using these allegations to justify continuing the operation on the Palestinian city of Rafah and prolonging the war for political purposes," the source said.

Israel's National Security Adviser, Tzachi Hanegbi told public broadcaster KAN on Wednesday that Israel must "ensure with the Egyptians that there is no smuggling through the tunnels" under the border.

Since 2013, Egypt has destroyed hundreds of cross-border tunnels with Gaza that it said were being used to transport militants and weapons during Cairo's years-long war with Islamist insurgents in North Sinai.

An Israeli official said Wednesday the military had established "operational control" over the strategic Philadelphi corridor along the border between the Gaza Strip and Egypt.

The buffer zone was designated by an agreement between Israel and Egypt.

Israel "must close the border between Egypt and Gaza", Hanegbi told KAN before the military announcement.

Since the deadliest ever Gaza war began in October, Israel has repeatedly alleged that smuggling continues to take place through tunnels under the border.

Egypt has accused Israel of using the allegations to justify illegally occupying the Philadelphi corridor, according to Egypt's State Information Service head Diaa Rashwan.

In January, Rashwan said Egypt had "eliminated these tunnels once and for all", including by creating a buffer zone and reinforcing the border, making "any smuggling operation impossible, whether above or below ground".

Tensions between Israel and Egypt -- which was the first Arab state to recognise Israel and has historically played a key mediator role -- have soared since Israel dismissed global warnings and sent ground troops into Rafah earlier this month.