Dani Alves admits Barcelona must sharpen up in Europe despite going top of their Champions League group with a 2-0 win over Dynamo Kiev.

With Rubin Kazan holding Inter Milan earlier in the evening, holders Barca took control of Group F after seeing off Dynamo at the Nou Camp thanks to goals in either half from Lionel Messi and substitute Pedro Rodriguez.

Barca were full value for the win and would have recorded a much more convincing scoreline but for the impressive display from Dynamo goalkeeper Olexandr Shovkovskiy.

However Pep Guardiola's side were still not at their best and were perhaps fortunate not to have conceded at least once.

"In the Champions League we are still giving away too many chances to our opponents. We have to try and ensure this doesn't happen," said Alves.

"They (Dynamo) made it difficult for us. We were slow in moving the ball around at the start.

"But we improved and we created chances. We had total control of the game.

"We are happy despite knowing that we can still get better."

Barca captain Carles Puyol also admitted that Dynamo, who had been unbeaten in 15 competitive matches heading into the clash, had made it tough for his side.

"It was a difficult match and maybe we weren't able to play our normal game," he said.

"We knew that they were very strong defensively, and who would look to hit us on the counter-attack. We picked up three very important points."

Puyol's central-defensive partner Gerard Pique added on his club's website: "Until Messi's goal we struggled to get on top.

"We weren't totally fluid in our play. It's not been our best day, especially with regards to moving the ball around."