Prime Minister Benjamin Netanyahu’s closest political ally has called for Israel to carry out a “thorough cleansing” of the Gaza Strip as a tenuous ceasefire between its Hamas rulers and the Jewish state frayed.

Speaking on Israel Radio, the far-right former foreign minister Avigdor Lieberman called for Israel to reconquer the crowded coastal enclave to avoid “finding ourselves in two years with Hamas having aircraft and hundreds of missiles that will reach beyond Tel Aviv”.

His comments came as the Israeli Air Force attacked targets in the Gaza Strip after six rockets were fired from Gaza into southern Israel into the early hours of Monday morning. No one was injured.

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Mr Lieberman suggested that neither the eight-day aerial campaign Israel launched in November with the stated goal of halting rockets from Gaza, nor the devastating Operation Cast Lead in 2008-09 in which more than 1,100 Palestinians and 13 Israelis died, had proven effective at quelling the violence.

“Without willingness to take things to their conclusion we merely increase the threats,” he said, adding that Hamas “has no intention of coming to terms with the Jewish presence in the land of Israel and therefore what is needed is to seriously consider conquering the Strip and carry out a thorough cleansing.” Mr Lieberman was number two on Mr Netanyahu’s electoral list during elections last January, and currently holds the post of chairman of parliament’s foreign affairs and defence committee. Mr Netanyahu’s office declined to comment on Mr Lieberman’s statements. Yair Lapid, the centrist Finance minister, said the remarks were “irresponsible”.

After the rocket fire, Israeli warplanes pounded what the military said were arms storage facilities and a rocket launch site in the Strip. There were no injuries from either the rockets or the air strikes. Israel ordered the closure of the Kerem Shalom and Erez crossings between Gaza and Israel, a step condemned as a “collective punishment” by Jaber Wishah, a spokesman for the Gaza City-based Palestinian Center for Human Rights.

Israeli army officials believe the rockets were fired by the Islamic Jihad group, a small militant faction currently at loggerheads with Hamas. But Israel said Hamas, which has controlled the Strip since seizing power there in 2007, bears overall responsibility.

Meanwhile, police said vandals slashed the tyres of 21 cars in the Arab Beit Hanina neighborhood of East Jerusalem in the latest of a wave of anti-Arab crimes by suspected Jewish extremists who have struck three times in and around Jerusalem in the past 10 days. Palestinian residents said the government was not doing enough to stop the vandalism. Police spokesman Micky Rosenfeld said police are treating the matter as a “high priority”.