UK Foreign Secretary William Hague has arrived in Baghdad to meet political and community leaders.
"As a friend of Iraq, the UK believes the urgent priority must be to form an inclusive government that can command the support of all Iraqi people and work to stop [Isis] in its tracks," he said.
Meanwhile, the Iraqi air force is reported to have launched an assault in
Air strikes
Mr Maliki told the BBC: "Yes, Syrian jets did strike Qaim inside the Syrian side of the border.
"There was no co-ordination involved. But we welcome this action. We actually welcome any Syrian strike against Isis... But we didn't make any request to Syria. They carry out their strikes and we carry out ours and the final winners are our two countries."
Unnamed US and Iraqi military officials told the Associated Press earlier that Syrian warplanes had bombed militants' positions inside Iraq on Tuesday.
A Pentagon source told BBC News: "We are aware of the reports that the Syrian government has taken strikes against targets in Iraq. We have no reason to dispute these reports."
Militant sources have been reporting for two days that Syrian jets hit the Iraqi side of Qaim, and also Rutba which is further inside Iraq.
The militants say 70 people were killed in the first attack and 20 in the second.
Jet delivery
Mr Maliki also said that Iraq had bought a number of used Sukhoi fighter jets from Russia and Belarus.
He said the aircraft could be flying missions in Iraq "within a few days".
Russian President Vladimir Putin discussed the crisis with Mr Maliki by phone last Friday, the Kremlin reported http://kremlin.ru/news/45950 at the time.
Mr Putin confirmed his "full support" for the government's efforts to rid Iraqi territory of "terrorists", it said, without giving details.
Mr Maliki said on Wednesday that forming a broad emergency government would go against the results of April's parliamentary elections, which were won by his alliance of Shia parties.
His political rival, Ayad Allawi, had proposed forming a national salvation government.
Reports say a unit of al-Qaeda's Syrian affiliate, the Nusra Front, pledged allegiance to Isis in the Syrian town of Albu Kamal, near the Iraqi border.
The Nusra Front, along with other rebel groups, has been fighting in Syria against Isis, which it sees as harming its cause with its brutality and extremism.
Also on Thursday, the leader of Iraqi Kurdistan visited the northern city of Kirkuk for the first time since it was seized by Kurdish forces earlier this month.
It fell into the hands of Kurdish fighters when Iraqi troops fled in the face of the Islamist advance.