By Eli Berlzon
SUFA, Israel (Reuters) - Israel's military said it had discovered a cross-border tunnel on Thursday built by the Islamist Hamas group from the Gaza Strip during a rare flare-up of violence along a border that has been largely quiet since a 2014 war.
Hospital officials said a 54-year-old woman had been killed in Gaza and one man wounded by fragments of an Israeli tank shell fired near Rafah during the violence, which erupted on Wednesday.
Israel's Shin Bet undercover intelligence agency said a Hamas operative arrested last month had provided useful information about the tunnel networks in the area, though it did not explicitly attribute Thursday's discovery to his data.
Militants fired mortar shells at Israeli forces working to unearth the tunnel and Israel responded with tank fire and air strikes, an army spokeswoman said.
Israeli aircraft targeted four Hamas positions in the vicinity of the tunnel, the military said. Over the past two days there have been 10 instances of Hamas fire against Israeli forces operating in the area, it added.
Hamas, Gaza's de facto ruler, has not confirmed responsibility for the shelling and did not comment on the announcement of the tunnel's discovery.
Lieutenant-Colonel Peter Lerner, a military spokesman, said the tunnel unearthed on Thursday was situated 28 meters (yards) below the surface and that an investigation was underway to determine whether it was dug before or after the war.
He said the militants may have started firing mortars at the Israeli forces to prevent them discovering the tunnel. Last month a first tunnel was unearthed without incident.
TRUCE UNDER THREAT
Gaza analysts said the flare-up of violence, the most intense since the 2014 war, threatened the truce that has largely held in the area for nearly two years.
A Qatari official in Gaza said efforts were ongoing to ensure the situation did not spiral out of control and a Hamas spokesman said Egypt was also trying to restore calm.
Israel has been wary about discussing what means it has employed to uncover the tunnels but the arrest of Mahmoud Atouna, 29, from Jabalya in the northern Gaza Strip early last month may have helped.
"Atouna provided his interrogators much information about the tunnel routes in the northern Gaza Strip, its tunnel-digging methods, the use of private homes and public buildings to bore tunnels and materials used," Shin Bet said in a statement on Thursday.
More than 2,100 Palestinians, mostly civilians, were killed during the 2014 Gaza conflict. Sixty-seven Israeli soldiers and six civilians in Israel were killed by rockets and attacks by Hamas and other militant groups.
(Additional reporting by Nidal al-Mughrabi in Gaza, Writing by Dan Williams and Ori Lewis; Editing by Gareth Jones)