Minister for Foreign Affairs Charlie Flanagan has said he is "disappointed and concerned" that the trial in Egypt of Irish citizen Ibrahim Halawa has been adjourned until December.

The trial has been put back until December 15th after two critically ill defendants failed to appear at a weekend hearing.

Mr Halawa, who has been detained since August 2013, is charged with taking part in a banned protest in Cairo July 2013.

He is one of 420 people charged with a range of offences. Charges against other people range from murder to attempted murder during a fatal attack on a police station in Ramses Square in central Cairo.

Speaking this morning, Mr Flanagan said: “I am both disappointed and concerned that this trial of the Irish teenager Ibrahim Halawa has not yet been concluded.

“We are engaged on a constant basis with the authorities in Egypt. Officials from the Irish embassy attended at his trial, reported back directly to me. I am very much involved in this case and have been since I was appointed to this position in the middle of last year.”

At the weekend hearing at Wadi Natrun about 100 kilometres south of Cairo, lawyers argued several clients who attended court were also ailing and submitted petitions for their admission to hospital.

Lawyers and family members attending the session were surprised and distressed over the length of the adjournment and protested the rule that all defendants in the case have to be present for a trial to proceed.

Mr Halawa and three sisters were detained at Fateh mosque in mid-August 2013. His sisters - Fatima, Omaima and Somaia - were released after three months on bail and permitted to return to Dublin but he has been detained in several prisons since his arrest.

Mr Flanagan said he is “very concerned that any citizen anywhere would be detained without trial for a period of two years”.

“I am very anxious that the trial be concluded at the earliest date and that Ibrahim Halawa be reunited with his family here in Dublin to resume his studies. We have conveyed concern at the highest level.”

“I note the application from his lawyers of his release. I understand this is an issue to be considered by the judge and I hope would be decided upon at the earliest opportunity.”