BUCHAREST (AFP) - Poland striker Robert Lewandowski was felled by a firework thrown from the crowd in a stormy World Cup clash on Friday but he had the last laugh, scoring twice in a 3-0 win over Romania.

Romanian fans threw the firework at the Bayern Munich star in the 53rd minute.

He needed medical treatment while referee Damir Skomina gathered the players from both sides inside the penalty area.

After play was briefly delayed, Lewandowski recovered to hit two late goals after 84 minutes and a last-gasp penalty.

On the terraces, fans from both countries launched flares at one another. Some thrown by home fans landed on the pitch, causing a delay just before the half-time mark.

Twelve Polish fans had already been arrested before the game after fighting in a city centre bar and clashes with police outside the stadium.

Around 4,000 police were mobilised for the high-risk game.