Tension is rising across the Middle East as Israel and Hamas, the Palestinian group which controls the Gaza Strip, continue to exchange fire amid the worst outbreak of violence since the Israeli assault on the territory nearly four years ago.As the death toll in Gaza reached 19, three Israelis were killed in the southern town of Kiryat Malachi on Thursday after a rocket fired from Gaza hit an apartment building.Israeli sources said two rockets hit the Tel Aviv area - one landed in the sea while another missile landed in an uninhabited area of Israel’s commercial centre.Air raid sirens sent residents running for shelter in Tel Aviv, a Mediterranean city that has not been hit by a rocket since the 1991 Gulf War.Islamic Jihad, another Gaza-based Palestinian group, said that it had fired one of the rockets that hit Tel Aviv.Late on Thursday, Israel began moving troops towards the Gaza Strip and Ehud Barak, the Israeli defence minister, authorised the call-up of 30,000 reservists for a possible ground operations.At least a dozen lorries carrying tanks and armoured vehicles were seen moving towards the border area, while buses ferried soldiers.While southern Israeli areas near Gaza have long coped with rocket fire, the attacks on the Tel Aviv area illustrated the significant capabilities that Hamas has developed.Palestinian fighters had previously hit Rishon Letzion before but never reached Tel Aviv, which is only 70km north of the Gaza Strip.At least 19 Palestinians, including two children, have been killed and more than 150 others wounded as of Thursday in fighting which began with an aerial attack that killed Ahmad Jabari, the Hamas military commander who was accused by Israel of overseeing attacks against civilians.