SOCHI, June 18 (Xinhua) -- Belgium coach Roberto Martinez felt very happy with the team's performance in their 3-0 win against Panama in the World Cup Group G opener on Monday.

"I'm so delighted. There are no easy games, but the players managed to win," Martinez said. "In the first half we started well for 10 to 15 minutes but they defended well with their defensive structure and we became a little frustrated in some situations where we would normally take a chance."

Panama staged a very encouraging performance at the start on their World Cup debut as they held Belgium's talented team to a 0-0 draw by halftime. But three beautifully crafted goals in the second half helped Belgium claim the hard fought victory.

"We didn't want to win it in the first five minutes, in the World Cup we understand that we need to play for 90 minutes. We need to be very aware in every game that if you don't score you must be prepared to work hard and to go through periods where your opponents test you.

"It was a moment to show maturity, it was a moment to show composure and real togetherness. I was very happy with the work of every single player. We need to grow. We grew in the second half and now we have to take it to the next game," the coach added.

Belgium will next face Tunisia on June 23 and then take on England on June 28.