A rocket launched from the Hamas-ruled Gaza Strip struck the Israeli port city of Ashkelon today, officials said, causing no casualties but prompting Israel to threaten retaliation with "great force".
There was no immediate claim of responsibility for the attack from Palestinian armed factions in the Gaza Strip, still reeling from a 22-day Israeli offensive that the Jewish state said was aimed at ending rocket salvoes.
Egypt, which also borders the Gaza Strip, has been trying with US backing to broker a long-term truce which would end Palestinian arms smuggling and also lead to reopening the coastal enclave's border crossings, one of Hamas's key demands.
Palestinians in Rafah, a town on the Gaza-Egypt frontier riddled with gun-running tunnels, said they received recorded phone messages warning them to avoid "terrorist figures and arsenals" - a possible precursor to retaliatory Israeli air strikes.
Ashkelon mayor Benny Vaknin told Israel Radio that a Grad rocket "struck the heart of a residential neighbourhood". It landed in an open area and caused no casualties.
Israeli right-winger Benjamin Netanyahu, who opinion polls forecast will become prime minister after an election a week away, said during a solidarity visit to Ashkelon: "The only way to remove the rocket threat is to topple the Hamas regime."
The Gaza assault ended with ceasefire declarations on January 18th. Some 1,300 Palestinians, including 700 civilians, were killed during the offensive, according to medical officials in Gaza, while Israel lost 10 soldiers and three civilians.
There has been some rocket and mortar shelling since, as well as a bomb blast that killed an Israeli soldier on the Gaza border. Militants said they were responding to Israeli fire.
Israel has carried out air strikes but held back from a renewed ground offensive during the recent surge of violence, in which three Palestinian civilians and a gunman were killed.
Israeli prime minister Ehud Olmert's government blamed Hamas for the violence, though Hamas has claimed responsibility for none of the attacks since the truce. "Hamas is playing with fire, and if there is going to be an escalation now, Hamas has no one to blame but itself," Olmert spokesman Mark Regev said. "Hamas has acted to deliberately undermine the calm."
The flareups highlight faultlines in Israel's coalition government ahead of the election to replace Mr Olmert next week.
Foreign minister Tzipi Livni, a centrist candidate, told Army Radio: "Deterrence must now be achieved vis-a-vis Hamas, and deterrence is achieved through force, and great force."
Her rival, centre-left defence minister Ehud Barak, has spoken out against launching a new offensive for now. "We dealt Hamas a very heavy blow, and it is now picking up the pieces. It really is interested in quiet, but the fire (from Gaza) is a fact and can't be ignored," he said in a statement.
Israeli media have suggested that any new reprisals could include the assassination of Hamas leaders, several of whom went to ground during the Gaza offensive and have yet to emerge.