British warplanes hit oil fields that help finance the activities of the Islamic State in Britain’s first airstrikes following a vote in Parliament that authorized military action in Syria, its defense secretary said Thursday. Defense Secretary Michael Fallon told BBC that the Omar fields in eastern Syria were targeted to strike “a very real blow at the oil and the revenue” on which ISIS depends. The strikes came within hours of Parliament’s vote to attack the terror group. Fallon confirmed that eight more jets were on the way to Britain’s base in Cyprus to join attacks and warned that military action against ISIS should be expected to continue for years to come. Four Royal Air Force Tornadoes took off from a British air base in Akrotiri, Cyprus, shortly after the 397-223 vote by lawmakers in the House of Commons. The RAF has been launching airstrikes against ISIS in Iraq since 2014. The decision to expand the campaign to Syria came after an emotional 10 1/2-hour debate in which Prime Minister David Cameron said that Britain must strike the militants in their heartland and not "sit back and wait for them to attack us." Opponents argued that Britain's entry into Syria's crowded airspace would make little difference, and said Cameron's military plan was based on wishful thinking that overlooked the messy reality of the Syrian civil war. Cameron has long wanted to target ISIS in Syria, but had been unsure of getting majority support in the House of Commons until now. He suffered an embarrassing defeat in 2013 when lawmakers rejected a motion backing attacks on the forces of Syrian President Bashar Assad. The mood surrounding the airstrikes changed following the Paris attacks in November, claimed by ISIS, that killed 130 people. Both France and the U.S. urged Britain to join the air campaign in Syria, and Cameron said Britain shouldn’t let its allies down. France welcomed the first British airstrikes in Syria Thursday, saying they are a sign of the European solidarity promised after the Paris attacks. President Francois Hollance said in a statement the British vote to begin airstrikes and the upcoming German vote on Friday were a sign that Europeans would stand together against the Islamic State. President Barack Obama welcomed the British vote to join the air campaign in Syria, saying the Islamic State group "is a global threat that must be defeated by a global response." Critics claim the British airstrikes will make no difference in the fight against ISIS, and that ground forces will be needed to root out the terror group. Britain has ruled out sending troops, and critics of the government have responded with skepticism to Cameron’s claim that there are 70,000 moderate Syrian rebels on the ground. --The Associated Press contributed to this report.