UEFA says a "technical issue" was behind the delays in implementing the VAR process during Wednesday's Champions League clash between Schalke and Manchester City.

Despite leading through Sergio Aguero's 18th-minute effort, City - who went on to win 3-2 - were behind at the break after Nabil Bentaleb scored a pair of spot-kicks.

The first of those was awarded by referee Carlos del Cerro Grande after a lengthy period of deliberation and confusion, with Nicolas Otamendi ultimately penalised for handball.

It took almost three minutes for that call to be made, and another two before Bentaleb sent Ederson the wrong way from 12 yards.

Five minutes later, Schalke had another penalty decision awarded following a VAR review, as Fernandinho bundled into Salif Sane at a free-kick.

UEFA released a statement on Thursday explaining that a problem with the pitchside monitor meant the officials had to use a backup process.

"When such a malfunction of the system occurs, the IFAB protocol allows for the VAR to describe to the referee what can be seen on the TV replay(s) but not tell him the decision that should be taken," read the statement. "The referee then makes a final decision based on his own perception and the information received orally from the VAR.

"In regards to the first decision, the inability to access the incident replays at the pitchside review area led to a delay in reaching the correct decision to award a penalty kick for a handball offence, while the VAR orally described the situation to the referee to allow him to make a final decision, and for the referee to then provide an explanation to the two team captains to clarify the circumstances regarding the pitchside review area and the decision-making process

"The second decision was also correctly made on the basis of the Laws of the Game (Law 11 – Offside) which stipulates: 'if a player in an offside position is moving towards the ball with the intention of playing the ball and is fouled before playing or attempting to play the ball, or challenging an opponent for the ball, the foul is penalised as it has occurred before the offside offence'."

UEFA chief refereeing officer Roberto Rosetti commented: "I am pleased that even without the possibility for the referee to review the incidents with his own eyes, the excellent cooperation of the team of officials led to correct decisions being made.

"It must also be underlined that - and as is described in the VAR protocol - accuracy is always in principle more important than speed when reaching a decision.

"Clearly, last night’s technical issues had a big impact on the time taken to reach decisions, but we are fully aware that reducing the time factor is key to the success of VAR and we are doing our utmost to make reviews as quick and efficient as possible.

"However, what we ultimately want is correct decisions in such match-changing situations and this is what we got yesterday."