JERUSALEM (Reuters) - Israel is preparing to build a network of sensors to try to detect tunnel building into its territory from the Gaza Strip, but it could take months to prove the technology works, a senior army officer said on Monday.
In the meantime, the army might re-invade the Palestinian enclave to destroy any tunnels it discovers or that it thinks are under construction, another official said, looking to calm the fears of Israelis living close to the Gaza border.
Israeli ground forces plowed into Gaza last month to demolish a warren of underground passages that Hamas Islamists had dug to infiltrate the border.
The army said it destroyed 32 of them, but believes some, which also serve as bunkers and weapons caches, survived intact.
After more than a decade of failed attempts to develop ways to reveal the infiltration tunnels, an army officer said the military was preparing to place sensors around Gaza's perimeter.
The army hopes these will not only be able to detect tunnels under construction, but also others already built.
In a briefing to reporters, the officer, who declined to be named, said the sensors would be augmented by physical obstacles placed along the 68 km-long (42 miles) frontier.
He did not discuss the technology, but said testing over the next few months would show whether it was ready for use. Previous experimentation has focused on seismic detectors.
Underlining Israel's anxiety to overcome the problem, the officer said an Israeli delegation had even traveled to Vietnam in 2002 to try to learn from how the Americans had dealt with guerrilla tunnels during the war in the 1960s and '70s.
Israel launched its Gaza offensive on July 8 with the aim of halting militant rocket barrages from the enclave, sending in ground forces days later to tackle the tunnels. The fighting has killed 1,938 Palestinians and 67 Israelis, and has devastated wide tracts of the densely populated Gaza Strip.
During the month-old conflict, militants infiltrated Israel several times and killed five soldiers at a lookout post.
The senior commander on Israel's southern front, Major-General Sami Turgeman, said on Monday it might take months before the sensor technology was proven.
"Until then, I propose that every time we discover that the enemy is building a tunnel, we will enter the area and destroy it," Turgeman told Israeli residents near the Gaza border.
Yedidia Yaari, the chief executive officer of Rafael Advanced Weapons Systems, a state-owned firm that produces the Iron Dome missile interceptor, told Channel 2 at the weekend that a solution to the tunnels threat was becoming more real.
"It is not simple to discover tunnels, but it is something that we are finding a solution for, and in my opinion it is close," he said.
One of Israel's concerns about the tunnels is that they might be used to abduct Israelis, as happened in 2006 when Gaza infiltrators grabbed soldier Gilad Shalit. They held him for over five years before freeing him in exchange for more than 1,000 Palestinians held in Israeli jails.
Late last month, Israeli officers feared that one of its soldiers had been seized by militants hiding in a tunnel and launched an immediate, massive barrage in southern Gaza in an apparent effort to prevent him being taken away from the area.
Some 70 Palestinians, many of them civilians, died in the shelling and the Israeli military said that a subsequent investigation had shown that the missing soldier was probably already dead before the barrage was unleashed.
The Association for Civil Rights in Israel (ACRI) on Monday urged the Attorney General to investigate the so-called "Hannibal Protocol", saying it was a disproportionate use of firepower that endangered the soldier and killed many civilians.
Israel instituted the procedure only for use against guerrilla groups, such as Hamas and Lebanese Hezbollah, which do not abide by the Geneva Convention on prisoners of war.
"A protocol that puts the life of the captured soldier in jeopardy to thwart a kidnapping is fundamentally unacceptable," ACRI said.
"The implementation of the Hannibal Protocol in populated areas fails to distinguish between civilians and combatants and causes needless suffering. It is our opinion that the use of this protocol ... constitutes an illegal method of warfare."
Writing by Ori Lewis; Editing by Crispian Balmer