Britain has completed its second wave of bombing raids on Islamic State targets in Syria against a backdrop of mounting concern that coalition military forces may also become drawn into airstrikes against the jihadis’ expanding enclave in Libya.

Four British warplanes – two Tornados and, for the first time, two Typhoons – struck wellheads in the vast Isis-controlled Omar oilfield on Friday night using Paveway IV guided bombs as part of the coalition’s strategy of impairing the terrorist group’s funding streams, the Ministry of Defence said. It described the operation as part of “daily missions”, suggesting more strikes were planned for Saturday night. Michael Fallon, defence secretary, repeated warnings that the UK would be engaged in action against Syrian targets for the long term. Speaking during a trip to RAF Akrotiri in Cyprus, where the aircraft striking Isis targets are stationed, he refused to offer a campaign timetable, stating that it was “not going to be short or simple”.

Facebook Twitter Pinterest RAF footage of British bombing raids on Friday.

An accompanying MoD statement said that RAF crews had conducted eight strikes on Friday, with initial intelligence indicating they were “successful”. It added that an RAF Reaper drone had also provided support to Kurdish security forces in north-west Iraq, destroying an Isis truck bomb close to the town of Sinjar.

Within hours of Fallon’s interview being broadcast, a man wielding a machete attacked several people at Leytonstone tube station, east London. He reportedly shouted, “This is for Syria” after he launched the attack, which police are treating as a terrorist incident. One man suffered serious knife wounds, which were non-life-threatening, while two other people sustained minor injuries. Police arrived within minutes of the attack beginning and the man was Tasered and arrested.

Meanwhile, there are indications that attention in the Middle East is already turning to Libya, where Isis is rapidly consolidating its power base. Speculation about coalition airstrikes in the troubled country intensified throughout last week after reports that France – one of the UK’s principal coalition partners targeting Syria – flew its first reconnaissance missions over the town of Sirte, joining the drones of the US, another key partner. Sirte has been taken over by Isis, with the UN estimating that there are 1,500 fighters in the town, while reports suggest its airbase is being prepared by extremists to take suicide planes.

Facebook Twitter Pinterest Michael Fallon at RAF Akrotiri in Cyprus confirms second British bombing raid.

Such developments have prompted disquiet among Libya’s neighbours. Italy’s foreign minister, Paolo Gentiloni, has announced an international summit in Rome to discuss the issue, admitting that he expects the next international emergency to emanate from the north African state, 300 miles to the south of Sicily.

To the west, Tunisia, shocked by the killing last month of 12 presidential guards by a Libyan-trained bomber, has shut its border with Libya and on Friday banned Libyan planes from the capital, fearing suicide attacks.

Among those concerned that Libya is becoming an increasing threat is France’s defence minister, Jean-Yves Le Drian, who has issued repeated warnings that the country is being used by Isis as a base to smuggle weapons to affiliated groups in Algeria and Mali and to the Islamist militant group Boko Haram in Nigeria.

Isis control and influence in Libya. Isis control and influence in Libya.

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On Saturday three suicide bombers, suspected of being from Boko Haram, attacked the island of Koulfoua on the Chadian side of Lake Chad, killing around 30 people and injuring 80. Chad extended a state of emergency in the region last month after five girls from Boko Haram detonated explosives in a suicide attack that killed 12 people.

Although the US has already struck Isis targets in Libya, including strikes in the town of Derna that the Pentagon claimed killed a prominent Isis leader, analysts warn that the possible loss of the town of Ajdabiya will critically destabilise the country’s economy.

Along with drones and spy planes, the US has bombers and helicopter-borne units stationed in Spain and Italy. RAF Tornados and Typhoons are also within striking range of Libya, as are jets on the French aircraft carrier Charles de Gaulle, currently stationed off the coast of Syria.