GAZA CITY, Gaza Strip (AP) — Gaza militants fired at least 10 mortar shells at Israel on Thursday, a day after Israel announced it successfully tested a high-tech shield against future mortar and rocket attacks from the Hamas-ruled territory.

Once installed later this year, the Iron Dome system could deprive Hamas of an important means of threatening Israel.

The Islamic militants have fired thousands of rockets and mortars at Israeli border communities over the years, causing relatively few casualties but sowing fear among hundreds of thousands of civilians in their range.

Israel’s announcement of the new rocket defense came as Egypt stepped up efforts to cut off hundreds of smuggling tunnels by building an underground steel wall along its border with Gaza. The tunnels help keep Hamas in power by bypassing a border blockade of Gaza imposed by Israel and Egypt.

On Wednesday, hundreds of stone-throwing Hamas loyalists clashed with Egyptian troops at the border. The two sides briefly exchanged fire, leaving an Egyptian guard dead and seven Gazans wounded, three of them seriously.

Egypt sent a stern message to Hamas. “Egypt warns that its patience has limits,” said Egyptian Foreign Ministry spokesman Hossam Zaki. “Any other attempt to provoke the Egyptian security will have its consequences.”

The underground wall and Israel’s missile shield could limit Hamas’ options in the future and pressure the militants to moderate, something it has refrained to do thus far. Hamas is engaged in indirect negotiations with Israel on a prisoner swap and with its Western-backed Palestinian rivals on a power-sharing deal. Hamas overran Gaza in 2007, seizing the territory from Palestinian President Mahmoud Abbas.

Ahmed Yousef, a Hamas official, shrugged off the latest developments.

“Hamas is not a state. It is a political resistance movement, and therefore it can adjust to any new circumstance,” he said, without elaborating.

On Thursday, Hamas-allied militants fired at least 10 mortar shells toward Israel, causing no injuries or damage. The militants said the mortar fire came in response to an Israeli air strike that killed a Gaza gunman and wounded several others earlier this week.

Three of Thursday’s mortars fell inside the Kerem Shalom crossing, the main conduit for goods to reach Gaza. Israel shut down the crossing in response to the mortar fire.

Israel and Egypt have kept Gaza’s borders virtually closed since June 2006, when Gaza militants captured an Israeli soldier. However, truckloads of medicine and basic foods are permitted to enter.

The Israel-Gaza border has been relatively quiet since the end of Israel’s three-week offensive against Gaza a year ago, launched to stop the rocket fire and subdue Hamas. Sporadic mortar and rocket attacks have taken place and have generally provoked Israeli military strikes.

Israeli military experts said the Iron Dome system would bring profound change to the volatile Gaza-Israel border.

“Until now, we were totally exposed to anyone in Gaza who had a rocket to shoot at Israel,” said Uzi Rubin, a former senior Israeli Defense Ministry official. “The ability to cause losses and casualties in Israel will be greatly diminished.”

Israeli media said the first anti-rocket battery is to be deployed in May near the Israeli border town of Sderot, the most frequent target of Gaza’s rockets.

Also Thursday, international activists delivered hundreds of tons of medicine and humanitarian aid to Gaza. The convoy was led by maverick British lawmaker George Galloway, who said the group “will be back with more (aid) until this criminal siege imposed on the people of Gaza, to punish them for how they voted in a free election, is lifted.”

Galloway lashed out at Egypt for the rough treatment he said members of the convoy had to endure en route to Gaza.

On Tuesday, the activists were confined by Egyptian forces to an area in the Egyptian port of El-Arish, amid disagreements over how many vehicles the activists could drive into Gaza. Dozens of foreigners and several members of the Egyptian security forces were hurt in clashes.

“Our arrival in El-Arish was the beginning of a nightmare,” Galloway said, adding that 55 members of his group had been hurt.