TEL AVIV — Palestinian militants unleashed a barrage of missiles at Israeli towns on Wednesday in revenge for a military incursion into the Gaza Strip that killed at least six, marking the first serious test of a 4 ½ month calm between Hamas and Israel.

Despite the sudden outburst, Israel and Hamas signaled Wednesday they prefer to hold to an Egyptian ceasefire, brokered this summer that halted daily cross-border attacks in Israel from Gaza, the coastal strip of 1.5 million Palestinians controlled by the Islamist group Hamas.

“We are contacting the Egyptian side to continue the calm,” said Fawzi Barhoum, a spokesman for Hamas in Gaza.

An escalation could create separate domestic political headaches for both Israelis and the Palestinians. It threatens Palestinian talks in Cairo next week aimed at mending the rift between President Mahmoud Abbas’ Fatah party and Hamas.

In Israel, a flare-up could dim prospects for Foreign Minister Tzippi Livni and the ruling Kadima party in an upcoming general election against Benjamin Netanyahu’s Likud Party. New hostilities could highlight in voters’ minds a perception that the current government has failed to provide security for residents of southern Israel.

An Israeli military spokesperson said the army counted more than 50 primitive Qassam rockets, mortars, and a Katyusha missile fired at population centers near Gaza on Wednesday.

The army sent ground troops into Gaza overnight with air cover to destroy what it says was a tunnel that was being readied to kidnap an Israeli soldier.

“Israel has no interest in an escalation of the situation in the south. On the contrary, we want to see the calm prevail,” said Mark Regev, a spokesperson for outgoing Israeli Prime Minister Ehud Olmert. “Hamas deliberately provoked this violence.”

WSJ.com