Following a week of non-stop Kassam fire, the IDF bombed a bridge leading to Kassam rocket launch sites in the northern Gaza Strip and conducted aerial strikes at access routes in the Sajaya area in the Gaza Strip early Friday. On Thursday the IDF began targeting specific locations across the northern Gaza Strip that have been used to fire the rockets, even at the risk of killing Palestinian police whose positions have generally been nearby the launch sites. The operation included artillery barrages as well as missiles fired from IAF aircraft and Navy warships. Overall, the IDF bombed at least ten Kassam launch site access routes. In the past, IDF artillery fire against Kassam rocket cells targeted empty fields in the vicinity of the launch sites but not the precise position of the launchers. On Thursday, the army warned the Palestinian Authority it intended to launch such strikes even at the risk of killing Palestinian security personnel stationed nearby. "We do not plan to begin bombing cities," a senior military source said. "But we are certainly stepping up our response and we are targeting the entire northern Gaza Strip with an emphasis on the precise launch spots." "If Palestinian security personnel are killed," the source continued, "it will be their problem." Defense Minister Shaul Mofaz ordered the IDF on Thursday to step up targeted killings and arrest raids against Islamic Jihad operatives behind Tuesday's first launching of a Katyusha rocket at Israel and the Kassam rockets fired on Thursday. One person sustained light wounds and several others were treated for shock on Thursday after a Kassam rocket fired from the northern Gaza Strip landed in a soccer field in Kibbutz Karmiya south of Ashkelon. The IDF response came quickly, as artillery shells and missiles fired from Navy warships stationed off the Gaza coast pounded the Kassam launch sites. Prior to the retaliatory attack, the army warned Palestinians security forces to evacuate their stations located near the northern Gaza Strip launch sites. "Katyusha rocket fire at Israel is grave and serious," Mofaz told defense officials during a weekly security assessment at the Defense Ministry in Tel Aviv. "It demands decisive and unequivocal action which will dismantle this terror infrastructure." Mofaz ordered the IDF and the Shin Bet (Israel Security Agency) to "get their hands" on those behind the Katyusha and Kassam attacks. He stressed the need to target those who planned the attacks, those who launched the rockets and those in possession of the weapons. During the security briefing, officials reported on a sharp increase in terror warnings, prompting Mofaz to extend an already-imposed closure on the West Bank and Gaza Strip. Later in the day, at a meeting with US envoys David Welch and Elliot Abrams, Mofaz said senior terrorists were entering the Gaza Strip through the Rafah border crossing with Egypt. Mofaz urged the Americans to intervene on Israel's behalf and to clamp down on security at the European-manned border crossing. Mofaz blamed Hamas, which he said was responsible for all that happened within the Palestinian Authority in light of the installation of the new PA government on Wednesday. Mofaz stressed that Israel would not be open to talks with Hamas unless the Islamist group accepted four conditions: annulment of its charter, acceptance of agreements reached in the past between Israel and the PA, recognition of Israel's right to exist and the dismantling of its terror infrastructure.