JERUSALEM -- Israeli-Palestinian tensions rose sharply on Wednesday, with a resumption of clashes over the Israel-Gaza border as Palestinian prisoners in Israeli jails declared a three-day hunger strike to protest the death on Tuesday of a fellow inmate, a death that the Palestinians blamed on Israel.
In response to rockets fired from Gaza into southern Israel, apparently in support of the Palestinian prisoners, the Israeli military said it carried out an airstrike in Gaza late Tuesday night, its first since a cease-fire that ended eight days of fierce cross-border fighting in November. Warplanes struck two open areas in northern Gaza, causing no damage or casualties, the military said.
Sami Abu Zuhri, a spokesman for Hamas, the Islamic militant group that controls Gaza, called the airstrikes a clear violation of the cease-fire. "We call on international parties to intervene immediately to end the Israeli escalation and also the violations against the prisoners," he said in a statement.
The rocket fire from Gaza was the third such violation of the cease-fire brokered by Egypt in November, evidence of its fragility. There have also been several episodes of gunfire from Israel directed at fishermen and farmers approaching newly relaxed security perimeters, sometimes with deadly consequences.
An Islamic extremist group in Gaza, the Mujahedeen Shura Council -- Environs of Jerusalem, claimed responsibility for the rocket fire, saying in a statement that it was in support of the Palestinian prisoners in Israeli jails. The group criticized other Palestinian factions for their inaction on the prisoner issue.
On Wednesday morning, Gaza militants fired two more rockets into southern Israel. One landed at the entrance of the Israeli border town of Sderot, according to the police, and the other fell in open ground. Neither caused injuries.
The tensions in the south came amid signs in the north of increasing spillover from Syria's bloody civil war. The Israeli military destroyed a Syrian post with tank fire on Tuesday night after shots were fired from the Syrian side at an Israeli Army jeep in the Israeli-held Golan Heights. Earlier that day, a mortar shell from Syria sailed over the Israeli-Syrian cease-fire line and crashed into an open field, according to the Israeli military.
The United Nations special coordinator for the Middle East peace process, Robert H. Serry, called the situation volatile and said it was "of paramount importance to refrain from violence in this tense atmosphere and for parties to work constructively in addressing the underlying issues."
"The renewed violations of the cease-fire risk undermining the 'understanding' reached between Israel and Gaza on 21 November, and unraveling the gradual but tangible improvements achieved since then in the easing of the closure and the security situation in Gaza and southern Israel," he said in a statement.
In a statement on Wednesday referring to the fire from both Gaza and Syria, Israel's defense minister, Moshe Yaalon, said, "We will not allow shooting of any sort, even sporadic, toward our citizens and our forces."
He added, "As soon as we identify the source of the fire, we will take it down without hesitation, as we did last night and in previous cases."
But analysts said that neither Israel nor Hamas appeared eager to escalate the situation and that both sides were acting to restore the calm.
The highly charged issue of Palestinian prisoners came to the fore again after the Palestinian leadership accused Israel of deliberately delaying the treatment of the prisoner who died, Maysara Abu Hamdiya, 64. He had received a diagnosis of throat cancer two months ago and died in an Israeli hospital on Tuesday.
Mr. Hamdiya, a resident of the West Bank city of Hebron and a retired general in the Palestinian Authority security services, was detained by Israel in 2002, at the height of the second Palestinian uprising, and was serving a life term for attempted murder after sending a suicide bomber to a cafe in Jerusalem, Israeli officials said. The bomb failed to detonate.
Mr. Hamdiya's death came amid efforts by the Western-backed Palestinian leadership to place the prisoner issue high on the diplomatic agenda, with the Obama administration calling for a renewal of Israeli-Palestinian peace talks. Emotions over the prisoner issue have been running high among the Palestinian public in recent months, leading to protests in support of prisoners on hunger strikes and over the death of a prisoner in February under disputed circumstances.
Israel's Ministry of Health said in a statement that an autopsy, held on Wednesday in the presence of a Palestinian expert in forensic medicine, showed that Mr. Hamdiya had died from complications of cancer and noted that he had been a heavy smoker, a factor that it said contributed to throat cancer.
The Palestinian Authority distributed a copy of an affidavit that it said was signed by Mr. Hamdiya's lawyer, Rami Alami, who visited the prisoner in jail on March 12. Mr. Alami said he found Mr. Hamdiya to be tired and weak and unable to walk without the assistance of other detainees.
Fares Akram contributed reporting from Gaza.
This article originally appeared in The New York Times.