Sirens sounded in Tel Aviv today, signalling a rocket attack on the city, and an explosion was heard, witnesses said.
A cloud of smoke was seen in the sky over the southern outskirts of Tel Aviv, Israel's commercial centre. No casualties were reported.
Israel Radio said it appeared that an "Iron Dome" anti-missile battery had intercepted the rocket in mid-air.
Hamas's armed wing in the Gaza Strip said it fired a rocket at the city, the third such attack since Israel launched its air offensive in the enclave on Wednesday.
Earlier, Israeli aircraft pounded Hamas government buildings in Gaza, including the prime minister's office, after Israel's cabinet authorised the mobilisation of up to 75,000 reservists, preparing for a possible ground invasion.
Hamas, the Islamist group that runs the Gaza Strip, said Israeli planes bombed the office building of prime minister Ismail Haniyeh - where he had met yesterday with the Egyptian prime minister - and struck a police headquarters.
Despite the violence, Tunisia's foreign minister arrived in the coastal enclave early today in a show of Arab solidarity, heading to a hospital to visit the wounded.
Rafik Abdesslem denounced the Israeli attacks on the Palestinian enclave as unacceptable and against international law.
"Israel should understand that many things have changed and that lots of water has run in the Arab river," Mr Abdesslem said as he surveyed Mr Haniyeh's office reduced to rubble in an overnight air strike.
"(Israel) should realise it no longer has a free hand. It does not have total immunity and is not above international law," he added. "What Israel is doing is not legitimate and is not acceptable at all."
Mr Abdesslem is the second high-profile visitor to Gaza since the start of the latest wave of violence, with Egyptian Prime Minister Hisham Kandil travelling to the territory on Friday.
In Washington, US President Barack Obama commended Egypt's efforts to help defuse the Gaza violence in a call to Egyptian president Mohamed Mursi yesterday, the White House said in a statement, and underscored his hope of restoring stability there.
Mr Kandil and Mr Abdesslem's appearance in the enclave reflects ever-stronger Arab solidarity with Gazans and their Islamist leaders following uprisings across the region, which have propelled Islamist-led governments to power in Egypt and Tunisia.
"The Arab League should bear its responsibilities to stop this flagrant aggression on our people in Gaza," Mr Abdesslem said.
Officials in Gaza said 38 Palestinians, half of them civilians including eight children and a pregnant woman, had been killed in Gaza since Israel began its air strikes. Three Israeli civilians were killed by a rocket on Thursday.
Rocket fire by militants into Israel resumed after dawn following a relative lull overnight, but the number was still lower than on the previous three days since the start of the offensive, an Israeli military spokesman said.
A three-storey house belonging to Hamas official Abu Hassan Salah was also hit and completely destroyed early Saturday. Rescuers said at least 30 people were pulled from the rubble.
The Israeli army said it had targeted a number of government buildings during the night, including Haniyeh's office, the Hamas Interior Ministry and a police compound.
Yesterday, Palestinians fired a rocket toward Jerusalem for the first time in decades. Tel Aviv, Israel's commercial centre, also came under rocket attack for the second straight day, in defiance of Israel's air campaign that began on Wednesday with the declared aim of deterring Hamas from launching cross-border attacks that have plagued southern Israel for years.
Hamas claimed responsibility for firing at Jerusalem and Tel Aviv. Israel said the rocket launched toward Jerusalem landed in the occupied West Bank, and the one fired at Tel Aviv did not hit the city. There were no reports of casualties or damage.
The siren that sounded in Jerusalem stunned many Israelis. The city, holy to Jews, Muslims and Christians, was last hit by a Palestinian rocket in 1970. It was not targeted when Saddam Hussein's Iraq fired missiles at Israel in the 1991 Gulf War.
Prime Minister Benjamin Netanyahu held a four-hour strategy session late yesterday with a clutch of senior ministers in Tel Aviv on widening the military campaign, while other cabinet members were polled by telephone on increasing mobilisation.
Political sources said they decided to more than double the current reserve troop quota set for the Gaza offensive to 75,000. It did not necessarily mean all would be called up.
Reuters