Diplomats and soldiers trapped inside Turkey's consulate in the northern Iraqi city of Mosul had no option but to surrender this week after hundreds of heavily armed Islamist militants surrounded the building, the foreign ministry said on Saturday.

The seizure by insurgents from the Islamic State in Iraq and the Levant (ISIL) on Wednesday of 49 Turks, including special forces soldiers, diplomats and children, has prompted criticism of Prime Minister Tayyip Erdogan's government for failing to foresee the danger and evacuate the consulate sooner.

The ISIL offensive threatens to dismember Iraq and leaves Turkey facing a widening Islamist insurgency in two of its southern neighbours, with ISIL also making territorial gains in Syria near the Turkish border.

Turkish Deputy Foreign Minister Naci Koru said every security precaution had been taken at the consulate but that events unfolded quickly and that Iraqi security forces stationed around the building abandoned their posts as ISIL seized Mosul.

"We gave an order (on Tuesday) to evacuate but our consul general told us that they were safer inside the consulate. He said it was not possible to evacuate under the circumstances," Koru told reporters in Ankara.

Hundreds of insurgents surrounded the building the next day, he said, at which point the consul general called Ankara again.

"The militants were asking them to surrender in 10 minutes and said otherwise they would come in. We contacted our prime minister and foreign minister immediately and the decision (to surrender) was made," Koru said.

"It wasn't possible to confront such a large group with the number of security personnel inside the consulate."

The militants entered the building and put the 49 people into vehicles before taking them to another location, where they are still being held and are unharmed, Koru said.

Some Turkish commentators have suggested the events could jeopardise Foreign Minister Ahmet Davutoglu's chances of replacing Erdogan as prime minister. Davutoglu is seen as a potential candidate for the job if, as expected, Erdogan decides to run for Turkey's presidency in an August election.

Erdogan said on Friday all efforts were being made to secure the release of the consulate staff, as well as a second group of 31 Turkish truck drivers also captured by ISIL this week. He criticised his opponents for trying to make political capital out of a highly sensitive situation.

No Plans For Military Strike

Turkish officials have made clear there are no immediate plans to launch any sort of military operation to release the hostages, saying relevant militant groups have been contacted and that diplomatic efforts are underway in co-ordination with NATO, the Iraqi government and the United States.

"Our first priority right now is the safe release of our citizens. There is no such thing on our agenda," Koru said, when asked whether Turkey would consider a military intervention.

No demands have been made by ISIL for the release of any of the 80 hostages, Koru added.

Iraq is Turkey's second biggest export market and largest oil supplier. The Turkish foreign ministry says an estimated 120,000 Turks are registered as resident in the country.

The vast majority of them reside in the autonomous Kurdish enclave which curves around north and east of Mosul and which so far has not been targeted by ISIL, serving as a buffer between the insurgents' advance and Turkish territory.

Turkey has urged its nationals to leave Iraq. Flag carrier Turkish Airlines is scheduling additional flights to Baghdad and Arbil, in Iraqi Kurdistan, to help them do so.

Davutoglu said on Friday there were no plans for a full evacuation but that a crisis centre with representatives of the foreign, economy, energy, transportation and customs ministries had been set up to keep track of Turkish workers in Iraq.

"We are standing next to our friendly neighbour ... We have so many areas of cooperation with Iraq and one of the decisions we have taken is that our cooperation will continue uninterrupted," he said.

"We are not planning a total evacuation ... According to our risk analysis, there is no such need."