Palestinian militants fired a rocket at Israel from the Gaza Strip on Thursday, killing a Thai farm worker, Israeli medics said, in the first death from a rocket attack since Israel's Gaza offensive last year.

Israel's emergency service said the man was about 30 years old and was working in an agricultural community just north of Gaza when he was killed.

A small Islamist faction calling itself Ansar al-Sunna claimed responsibility for the attack. A second group, the Al-Aqsa Martyrs Brigades, also later claimed responsibility.

Thursday's attack came on the same day as a visit to Gaza by Europe's top diplomat, EU foreign policy chief Catherine Ashton, who had just crossed into the territory when the rocket was fired.

"I condemn any kind of violence. We have got to find a peaceful solution to the issues and problems," she said.

United Nations Secretary General Ban Ki-moon also condemned the attack.

"All such acts of terror and violence against civilians are totally unacceptable and contrary to international law," he said in a statement.

In a statement emailed to reporters in Gaza, the Ansar al-Sunna faction said the attack was a response to Israel's "Judaization" of Islamic holy places in Jerusalem and elsewhere in the West Bank.

Israel's military said it was the third rocket fired from Gaza in a 12-hour stretch. There was no immediate Israeli retaliation.

Thousands of crude rockets launched from Gaza at Israel over a seven-year period sparked the Israeli military's three-week offensive in the Gaza Strip. The brief war devastated the Palestinian territory, killing 1,400 Palestinians, including hundreds of civilians. Thirteen Israelis were killed.

Rocket attacks and border ambushes have dropped dramatically since the war, but have not come to a complete halt.

Ashton was touring Gaza to get a firsthand look at the hardships caused by the war and by a punishing Israeli-Egyptian border blockade that has been in place since Hamas' violent takeover of Gaza in 2007.

After her Gaza visit, Ashton is to attend a major Mideast meeting of the so-called Quartet of Mideast mediators — the United States, the United Nations, Europe and Russia — in Moscow on Friday.

With files from CBC News