Israel has revealed the construction of a sensor-equipped underground wall alongside the 60km border with the Gaza Strip, which it described as a counter-measure to Hamas tunnels leading outside of its coastal territory.

Israeli media published new disclosures by the military on Thursday about the project, costing $1.1bn and to be completed within two years under an accelerated schedule.

The underground wall, which will be built from concrete and be fitted with sensors, is expected to reach dozens of metres deep into the ground and to stand at six metres high from ground level.

Israel has described it as a territorial counterpart to its Iron Dome short-range rocket interceptor, capable of blunting Hamas' limited means of challenging its superior armed forces.

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The Israeli Haaretz newspaper reported that in recent months, Israel had brought foreign labourers and contracted companies to flatten the area around the border.

"I think the other side will have to re-evaluate the situation in view of the barrier's construction," said the chief of Israel's southern command Major-General Eyal Zamir.

"If Hamas chooses to go to war over the barrier, it will be a worthy reason (for Israel) to go to war over. But the barrier will be built."

Hamas accused Israel of belligerence.

The unusually detailed Israeli threat followed a rocket launch on Tuesday which caused no damage in Israel and went unclaimed by Palestinian groups. Israel responded with an air attack on a Hamas facility that medics said wounded seven people.

Such flare-ups have been relatively rare since the last Israeli offensive on Gaza in 2014, with Hamas mostly holding fire and reining in smaller armed factions.

But as Gaza's poverty and political drift deepens, both sides worry that another conflict could erupt.

'Legitimate military targets'

Israel also said it had mapped armed emplacements hidden under civilian sites in the Palestinian enclave that may be attacked in any new war.

The military published aerial photographs and coordinates of two Gaza buildings that it said Hamas was using as cover for tunnel networks. One of these, it said, is a Hamas member's family home, linked to a mosque by a secret passage.

"These two targets, as far as I'm concerned, are legitimate military targets, and in the event that a new war begins, anybody in them is endangering himself, his family, and the responsibility [for their wellbeing] will fall on Hamas," Zamir said in a separate briefing to foreign journalists.

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A Hamas spokesman, Fawzi Barhoum, called the Israeli statements "lies and fabrications that aim to damage the image of the Palestinian resistance and justify the mass killing of thousands of Palestinians civilians".

More than 2,100 Palestinians, most of them civilians, were killed in the 2014 war, according to the Gaza health ministry. Sixty-seven Israeli soldiers and six civilians in Israel were killed.

A new buffer zone within Israel's territory, dozens of metres in width, will afford it extra time to respond by depriving Hamas tunnelers during war of targets on the frontier.

Israeli media said on Thursday that the military also planned to build an underwater barrier in the Mediterranean to prevent infiltration from Gaza by sea.