Islamic State has expanded since the start of US-led air strikes last September, Syrian President Bashar al-Assad has said.
Asked how effective the strikes had been in fighting the terror group, Assad told CBS: "Sometimes you could have local benefit but in general if you want to talk in terms of ISIS, actually ISIS has expanded since the beginning of the strikes."
Assad claimed that there were some estimates that IS was attracting 1,000 recruits a month in Syria.
He also warned the group were expanding into new territory in Iraq and Libya.
The Syrian president - who has been involved in a brutal civil war with rebels since 2011 - said he would leave power when he no longer retained public support, or felt he could not represent "the Syrian interests, and values."
Members of the US led coalition struck targets in Iraq and Syria overnight as part of the fight against Islamic State militants, according to the combined joint task force.
The attacks struck 14 targets in Iraq and one in Syria, including positions held by militants near the cities of Mosul, Tikrit and Fallujah.
Fighters and a monitoring group have said Islamist groups including al Qaeda's Nusra Front have seized the Syrian city of Idlib for the first time since the conflict in the country began.
By taking Idlib, the capital of a northwestern province of the same name, the insurgents now control a second province after Raqqa, a stronghold of the Islamic State group and target of US-led air strikes. Syrian officials could not be immediately reached for comment.
Britain will provide military training to "moderate opposition forces" in Syria, the government has announced.
Defence Secretary Michael Fallon said the UK would send around 75 military trainers and headquarters staff to instruct fighters on the use of small arms, infantry tactics and medical skills.
The training, which forms part of a US-led programme to support the moderate Syrian opposition, will be held in neighbouring Turkey and is expected to begin in the next few weeks.
Nine British medical students have reportedly travelled to Syria to help wounded people.
Some of the parents of the five men and four women, aged in their late teens and early 20s, are said to have travelled to Turkey this weekend in a bid to get them back.
The students, who reportedly flew to Istanbul from Sudan earlier this month, went to the region "to help, not to fight", a Turkish politician assisting the families told The Observer newspaper.
Mehmet Ali Ediboglu said the students were born and raised in England, but had been studying medicine in Sudan as their families had wanted them to experience a more Islamic culture.
He told the paper he thought the students had been "cheated, brainwashed".
He said: "Let's not forget about the fact that they are doctors; they went there to help, not to fight. So this case is a little bit different."
One of the women informed her family of the trip via the messenger Whatsapp, the paper reported.
Lena Maumoon Abdulqadir reportedly told her relatives: "Don't worry about us, we've reached Turkey and are on our way to volunteer helping wounded Syrian people."
A Foreign Office spokesman said it was working with Turkish police to try and track their whereabouts.
The families of those children who leave the UK to join Islamic State should take "prime responsibility" for their actions and not blame the security services, one of Britain's most senior anti-terror officers has said.
Greater Manchester Police's Chief Constable Sir Peter Fahy said it was "ill-advised" for the relatives of children who join terrorist groups to blame the police for not taking action.
Speaking to The Times, Sir Peter said:
What is ill-advised is to just blame the police, blame the authorities, blame the school, when the absolute prime responsibility for the welfare of children lies with parents. I'm not saying that is easy. But it creates the conditions.
Five teenage girls who have shown an interested in travelling to Syria have been barred from going abroad by the High Court.
The girls, two aged 15 and three aged 16, were made wards of court, which means they cannot leave the jurisdiction of England and Wales.
...the risk contemplated here is as grave as it can be for it is common knowledge that so many have lost their lives in Syria and so many have gone knowing that would be likely.
As I said early this week in another case, and I repeat it in this, sometimes the law has to intervene to protect these young people, ultimately from themselves.
Mr Justice Hayden ordered the removal of the girls passports, and those of a number of adults involved in their care. The judge, who made a similar order in relation to a 16-year-old boy earlier this week, said that it was a "draconian" step, as was the removal of a passport.
Syria's state news agency SANA said government air defences brought down a US surveillance drone in the coastal province of Latakia as officials condemned America for violating the country's sovereignty.
The US confirmed it had lost contact with an unarmed Predator drone over Syria, but stopped short of confirming it was shot down by Syrian air defences.
ITV News Correspondent Dan Rivers reports: