Belgium's Dries Mertens celebrates after scoring a goal against Algeria during their 2014 World Cup Group H soccer match at the Mineirao stadium in Belo Horizonte June 17, 2014. [Photo/Agencies]

BELO HORIZONTE - Much-fancied Belgium suffered a case of stage fright in their first World Cup match in 12 years and had to battle back from a goal down to beat gutsy Algeria 2-1 with two goals late in the game in their World Cup Group H opener on Tuesday.

Substitutes Marouane Fellaini and Dries Mertens saved Belgium's blushes after Algeria playmaker Sofiane Feghouli had put the North Africans ahead with a 25th minute penalty at the Mineirao stadium, their first World Cup goal in 28 years.

"It was a tough match but we were patient throughout and at the end we were rewarded," said Belgium coach Marc Wilmots, who was the last Belgium player to score in a World Cup until Tuesday.

"We stayed calm after doing a small mistake in the first half. We got a new momentum. We saw that Algeria were getting more and more tired. At half-time people were a bit down, but I said 'don't worry, we will score and we will change totally the match'."

Belgium, who next play Russia before taking on South Korea, are among the favourites for the tournament, breezing through the qualifiers unbeaten and bringing a team to Brazil with world class players such as Eden Hazard and Romelu Lukaku.

Yet they showed none of their skills and pace in a below-par first half performance in their first World Cup since 2002, with the pair completely shut out and the Algerians hardly putting a defensive foot wrong.

The North Africans, with key forward Islam Slimani surprisingly on the bench, posed little threat up front until left back Jan Vertonghen clumsily brought down Feghouli after a fine cross from Faouzi Ghoulam in the 25th minute.

Goal drought ends

Feghouli calmly sent keeper Thibaut Courtois the wrong way to end his country's 28-year wait for a World Cup goal and send the green-white-clad Algerian fans delirious.

Algeria, who have never advanced past the group stage, had last scored in a World Cup in 1986 in a 1-1 draw against Northern Ireland.

Belgium's Axel Witsel tried his luck with a couple of long-range shots but the Red Devils looked nothing like the menacing team that many consider can go all the way in the tournament.

Wilmots took off lacklustre Lukaku early in the second half, bringing on teenager Divock Origi to add pace to their game and instantly breathed new life into his team.

The 19-year-old, who became the youngest Belgian to appear in the World Cup, raced clear but failed to beat keeper Rais Mbohli with Algeria firmly on the backfoot.

It was Wilmots' other substitute, Fellaini, who delivered, rising high to meet a cross from man-of-the-match Kevin De Bruyne cross and send his glancing header off the bar and into goal on 70 minutes.

"To be honest I am not satisfied with the first half," De Bruyne said. "Algeria played very good with a good organisation. In the second half they allowed us more space and I can be very dangerous with my passing and crosses."

The Desert Foxes, lacking depth in their squad, gradually ran out of steam and were caught napping 10 minutes later when Hazard raced down the left and cut back perfectly for subsititute Mertens to fire home.

"It's a major disappointment," said Algeria coach Vahid Halilhodzic. "I would have liked to have a couple of tougher and more resilient players to resist their attacks but I don't have much of a choice."

"We missed a great opportunity here. But in the second half it was a bit tough. We left too much space to the Belgian team and the two goals scored against us were to be expected."