LONDON — Within an hour of the House of Commons' vote to carry out airstrikes against Islamic State (ISIS) targets in Syria, jets were in the air.

Royal Air Force Tornado planes hit their first targets inside of Syria, the Ministry of Defence confirmed in a statement on Thursday morning.

The GR4 planes hit oilfields in the eastern part of Syria, 35 miles from the border with Iraq.

"The Omar oilfield is one of the largest and most important to Daesh’s financial operations, and represents over 10% of their potential income from oil," the MoD said. Several of the oilfields have already been hit by the U.S.-led coalition.

"Our initial analysis of the operation indicates that the strikes were successful."

"This strikes a very real blow at the oil and the revenue on which the Daesh terrorists depend," Defence Secretary Michael Fallon told the BBC.

Fallon said that eight more jets were on their way to Britain's base in Cyprus to join attacks and warned that military action against ISIS should be expected to continue not for months, but years.

Ministers will make a Commons statement updating MPs on strikes in Syria before the Christmas recess, Grayling says. — Tim Sculthorpe (@timsculthorpe) December 3, 2015

Members of Parliament voted Wednesday night in favour of extending British airstrikes from Iraq to Syria. There were noisy protests outside in Parliament Square as thousands of demonstrators gathered to object to Prime Minister David Cameron's plan.

On Thursday, the hashtag #prayforsyria was trending in the UK with Twitter users reacting to the announcement that airstrikes had started. Some expressed disgust and disappointment, while others were critical of the outrage.

Additional reporting by The Associated Press.