Rocket kills 1 in Israel while Ashton in Gaza

It was the first strike from the territory to cause any fatalities since the end in January 2009 of Israel's Gaza war.

An hour before the attack, the EU's top diplomat, Briton Catherine Ashton, crossed into the Gaza Strip to tour U.N. facilities and see how the international funding was being used.

A previously unknown Gaza group, Ansar al-Sunna, claimed responsibility for the attack, launched a day before the international Quartet of Middle East peace mediators was to meet in Moscow to discuss ways to revive Israeli-Palestinian talks.

Similar strikes since the Gaza war have been met by Israeli air raids against militants or suspected weapons-producing facilities, but the death of the Thai worker, in Netiv Ha'asara, an agricultural community, may harden Israel's response.

"This is a crossing of the red line, which Israel cannot accept. The Israeli response will be appropriate. It will be strong," Vice Prime Minister Silvan Shalom told reporters.

At a Gaza news conference after the attack, Ashton said: "I condemn any kind of violence, we have got to find a peaceful solution to the issues and problems."

U.N. Secretary General Ban Ki-moon also expressed his condemnation, saying in a statement: "All such acts of terror and violence against civilians are totally unacceptable and contrary to international law."

The incident could have more of an impact on internal Palestinian politics than on the Middle East peace process, which Hamas has refused to join and which is at an impasse over Israeli settlement policy on land Palestinians want for a state.

Hamas Islamists, who seized the Gaza Strip in 2007, had been urging other militant groups not to mount attacks on Israel, voicing concern about retaliation.