JERUSALEM -- Rockets and mortars from the Gaza Strip pummeled southern Israel early Wednesday and an Israeli airstrike killed a Palestinian militant, in a sharp escalation of violence following a landmark visit to Gaza by Qatar's leader.

Another Gaza man died Wednesday of wounds sustained in an Israeli air attack the night before, a health official said. The deaths bring to four the number of Palestinians who have died in strikes on Gaza in the past two days.

Several foreign workers were wounded in the rocket fire Wednesday, and a number of militants were wounded in the Israeli air attacks, Israeli and Palestinian health officials said. Hamas security forces were ordered to evacuate their facilities for fear they would become targets of Israeli airstrikes, and some schools in southern Israel and Gaza canceled classes.

Crossings between Gaza and Israel were shut down following the exchanges of fire.

The Israeli military said 60 rockets and mortars were fired by early morning, and that Israeli aircraft struck Gaza three times. The Popular Resistance Committees said one of its members died in one of the airstrikes, and Gaza health official Dr. Ashraf al-Kidra said another Gaza man died of wounds sustained in an attack Tuesday night that killed two militants. No militant group claimed him as a member.

One of the rockets hit a house, causing no injuries, and one of the airstrikes struck a mosque in the southern Gaza village of Khouza for the second time in several weeks.

Hostilities have been simmering for weeks, and Israel's defense minister vowed that his country would not reconcile itself to attacks from Gaza.

Asked if Israel was considering a ground operation in the Palestinian territory, Ehud Barak told Israel Radio that "if we need a ground operation there will be a ground operation. We will do whatever necessary to stop this wave" of violence.

Much of the fighting has been between Israel and smaller militant groups. But the military wing of Gaza's Hamas rulers and a smaller militant group claimed credit for the rocket and mortar fire Wednesday.

In a statement, Hamas and the Popular Resistance Committees said "these holy missions come in response to the repeated, continuous crimes of the enemy against our people, which killed four and injured 10 in the past 48 hours."

The barrage from Gaza came just hours after Qatar's ruler accorded Hamas unprecedented political recognition by becoming the first head of state to visit the largely shunned Palestinian territory on Tuesday.

The emir, Sheik Hamad bin Khalifa Al Thani, also promised his oil-rich country would invest hundreds of millions of dollars in construction projects, something that would help to revive flagging popular support for Hamas by generating thousands of jobs in the destitute territory of 1.6 million people.

Israel's border with Gaza has been largely quiet since a major Israeli offensive four years ago, but violence has flared sporadically since.

Despite the recent flare-up, neither side appeared interested in a renewal of large-scale hostilities, and Hamas has largely stayed out of direct confrontation with Israel since the 2009 war. But it is also under pressure from various militant groups, including al-Qaida-inspired Salafis active in Gaza, to prove it remains in confrontation with Israel, whose existence it rejects.

Associated Press