BERLIN (Reuters) - German Chancellor Angela Merkel will go before parliament on Tuesday to explain the governments Afghanistan strategy in the face of mounting criticism from opposition parties weeks before a federal election. Berlin has come under intense pressure following a decision by its troops on Sept. 4 to call in an air strike on two fuel trucks near Kunduz which an Afghan rights body has said killed 60-70 civilians. The strike was the most deadly operation involving German troops since World War Two and was condemned by several European foreign ministers at the weekend.But Germany has said it was necessary to protect its troops from a possible suicide attack by Taliban fighters who had hijacked the trucks. Merkel, who has been criticised at home for not doing enough to convince Germans of the importance of the mission, called on Sunday for a quick, comprehensive and transparent probe of the strike, which was carried out by a U.S. F-15 fighter jet. A govt spokesman said Merkel would go before parliament following demands by opposition parties that she explain the incident and govt strategy in Afghanistan. Germans remain highly sceptical of military operations more than 60 years after the defeat of the Nazis. It was only a decade ago that German troops participated in their first foreign combat mission since the war. And polls show about two-thirds of Germans would like the 4,200 German troops operating in Afghanistan as part of a six-year old NATO mission to return home. But the military presence there has not been a big issue in the election campaign so far because Merkels conservatives and their chief rivals, the centre-left Social Democrats (SPD), both agree that the troops must stay. The far-left Linke, or Left party, has called for a demonstration against the war at the Brandenburg Gate on Tuesday and the head of Germanys Free Democrats (FDP), the party Merkel hopes to govern with after the Sept. 27 election, criticised the government on Monday for poor communication on the air strike. We are hearing very different things from different governments across the world, including from our allies, said FDP leader Guido Westerwelle, calling the lack of information from Merkels coalition unacceptable.The government has said that according to its information 56 people were killed in the strike, but that there is no proof any of these were civilians. Defence Ministry spokesman Thomas Raabe said on Monday that the decision to call in the strike was based on information from multiple sources which pointed to the presence of armed Taliban fighters near the tankers. He rejected suggestions that a German reluctance to shoot first in combat was behind a decision not to send ground troops to secure the fuel trucks, which were stopped in a river bed. Based on the information we have, we believe this strike was right and the suggestion that we are not capable of fighting (ground) battles is ridiculous, said Raabe at a news conference where he was grilled for 1-1/2 hours about the strike. You must realise we are talking about the middle of the night, with special visibility conditions, where we dont know what the enemy is planning. Therefore I think the decision that was made at the time was absolutely correct, he said. McChrystal, the top U.S commander in Afghanistan, issued new orders in July that were supposed to limit civilian casualties by requiring troops to take extra steps before opening fire.