A recent spate of cross- border and mortar attacks by Palestinian militants in the Gaza Strip -- the worst in a year -- is testing Israel's resolve to strike back hard against such provocation. But it remains to be seen whether the get-tough approach will hinder or escalate violence, analysts and officials said Friday.

Israeli military planes struck several Gaza targets early Friday, including what Israeli officials described as the first air attack on Gaza City in nearly a year.

Three Palestinians were killed, including a 14-year-old boy working inside an Egypt-to-Gaza smuggling tunnel targeted in the raid, Palestinian officials said. The tunnels are used to import weapons to Gaza and help sneak militants into Israel.

Israel said it was retaliating for the firing a day earlier of nearly a dozen mortar rounds and one Kassam rocket into southern Israel. The attacks, on various locations near the Gaza border, caused no casualties.

The longer-range Kassam rocket hit near the city of Ashkelon, the farthest strike from the seaside enclave since Israel's three-week offensive in Gaza last winter, officials on both sides said. Gaza is under the control of the Islamic militant group Hamas.

Israel launched that operation after repeated cross-border rocket attacks by Hamas and other militant groups based in Gaza. Experts said it was unclear whether the recent volley of air attacks marked a crack in the cease-fire between Hamas and Israel or was an isolated outburst.

"It's a very worrying phenomenon," said retired Israeli military commander Jonathan Fighel. "There is a need for both sides to remain calm and maintain the cease-fire."

He said the standoff marked one of the first major tests of an Israeli deterrence strategy, adopted after the Gaza offensive, to retaliate immediately and strongly to rocket strikes against southern Israel. Previously, Israel sometimes waited weeks or months to react.

"The shift in strategy is to hit hard to show that Israel is not going to sit quietly while its cities are attacked and that those who attack will pay a heavy price," Fighel said.

But representatives of an armed wing of the Popular Resistance Committees, which claimed responsibility for the mortar strikes, vowed to respond to Israel's attack with more violence.

"We will meet escalation with escalation, shelling with shelling, and we have the right to choose the correct time and place to do so," according to a statement from the group, quoted by the Palestinian news agency Maan.

Later Friday, three mortar rounds reportedly were fired toward Israeli positions east of the Rafah checkpoint.

Hamas has attempted to discourage other armed groups in Gaza from attacking Israel unless they are attacked first. The Popular Resistance Committees said its mortar barrage Thursday came in response to an Israeli drone strike earlier in the week that killed one of its leaders.

Hamas officials Friday accused Israel of inciting violence. "The Israelis don't need an excuse to attack us," said Ismail Radwan, a Hamas spokesman. "But these attacks will not terrify or shake us. We will respond to all attacks."

Shalom Harari, an Israeli counter-terrorism expert, said the attacks against Israel might also reflect growing divisions in Gaza among Hamas and rival Islamist groups, some of which have continued to launch sporadic strikes.

"It might be a test for [Israel], but it's also a test for Hamas and its system of control," said Harari, a former Defense Ministry advisor who now works at Israel's International Institute for Counter-Terrorism. "They might be trying to see how Hamas will react."

Hamas, he said, is probably not interested in resuming hostilities with Israel at this time. The group is angry at the government of Egypt over construction of a wall aimed at blocking tunnels used to bring weapons and goods through Egypt into Gaza, whose borders have been sealed by Israel and Egypt since Hamas seized control of the Palestinian territory in 2007.

Hamas is also engaged in negotiations with Israel over the possible release of Israeli soldier Gilad Shalit, who was captured by Hamas-affiliated militants in June 2006.

"I don't see a lot of passion from Hamas to try to widen the front," Harari said. "I don't think they feel prepared for another clash with Israel."

edmund.sanders@latimes.com