RAF Tornado jets have carried out their first air strikes against the self-styled Islamic State in Syria, the Ministry of Defence has confirmed.
Four Tornados from RAF Akrotiri in Cyprus took part in the operation soon after MPs voted to approve bombing.
The "successful" strikes hit the IS-controlled Omar oil fields in eastern Syria, the defence secretary said.
But PM David Cameron said the campaign would take time, saying "we're going to need to be patient and persistent".
"It is complex and it is difficult what we are asking our pilots to do, and our thoughts should be with them and their families as they commence this important work," Mr Cameron said.
MPs overwhelmingly backed UK military action against IS - also known as Daesh - in Syria, by 397 votes to 223, after a 10-hour Commons debate on Wednesday.
Defence Secretary Michael Fallon said the MoD would be assessing the damage done by the bombing later, but the aim was to strike "a very real blow on the oil and revenue on which Daesh depends".