Republic of Ireland manager Martin O'Neill has admitted that his side must improve if they are to qualify for the European Championship in 2016.

The Green Army fell to a 5-1 defeat to Portugal on Tuesday evening, and despite an improvement in the second half, O'Neill has insisted that they can't afford the same number of mistakes when their Euro 2016 qualification campaign begins in September.

The former Celtic boss is quoted by RTE Sport as saying: "I thought that we started nervously, and that was something we wanted to try to avoid. Two of their goals came from our possession, which we gave away needlessly.

"Those are the things that over the course of the European Championships you have to try and cut out. I thought we came to grips with it - we got the goal back and looked dangerous at times.

"We were still trying to chase it to get back to 3-2. When I finally sit down and analyse it, there should be things I am happy about and obviously things we need to improve."

O'Neill has won just one of his seven matches in charge of Republic of Ireland.