Two Palestinians have been killed by an Israeli airstrike in Gaza.

The attack was on a car travelling along a coastal road near a beach refugee camp in Gaza. 

One source identified the men as belonging to the Popular Resistance Committees, a network of groups that has been responsible for firing rockets into southern Israel.

Earlier, five Palestinians in Gaza were wounded by Israeli tank fire in response to the detonation of a border bomb.

A spokesman for Gaza's health services, Ashraf al-Qudra, said the five were hurt after the tanks targeted "two mosque minarets" east of Khan Yunis in southern Gaza.

An 11-year-old boy was in serious condition from that attack, he said.

The Israeli military said "an explosive device was activated against (army) forces operating adjacent to the security fence in the southern Gaza," causing no injuries.

"The force responded with tank fire towards lookout posts used to guide the attack against the forces," it said.

An army spokeswoman said nine explosive devices were set off at Israeli forces near the border with Gaza since the beginning of the year.

While there has been no recent rise in roadside explosions near Gaza, there has been an increase in Palestinian rocket fire at Israel in recent weeks, leading to air strikes by Israel.

The violence comes a day after Israel accused two men it said belong to Hamas of kidnapping three Israeli teenagers in the occupied West Bank a fortnight ago.

Israeli troops are staging a wide-ranging manhunt for two teenagers and an adult who disappeared from the southern West Bank on 12 June.

Meanwhile, Italy has advised its citizens not to invest in Israeli settlements built on occupied Palestinian land, just days after France issued the same warning.

Foreign Minister Federico Mogherini cautioned Italians "not to get involved in financial activity and investments" in settlements in the occupied West Bank, Gaza and East Jerusalem, according to La Stampa daily.

The warning, given "in accord with other European countries", comes as Italy "implements a political decision taken earlier," Mogherini was quoted as saying.

The international community regards all Israeli settlements built on occupied Palestinian land as illegal.

France advised its citizens earlier this week to avoid financial investments in the areas in question, following similar warnings on the British and German foreign office websites.