Embassy attack spreads Libyan instability to capital TRIPOLI (Reuters) - Libya's central government has long had only a tenuous grip on the eastern city of Benghazi, but the bombing of the French embassy in Tripoli shows its control of the capital may now also be under threat. The early morning car bomb devastated France's embassy, wounding two French guards, in the most significant attack against foreign interests in Libya since September's deadly assault on the U.S. diplomatic mission in Benghazi. The U.S. ambassador and three other Americans were killed in the Benghazi attack leading to a lingering political row in Washington with Republicans accusing President Barack Obama's administration of withholding information and the White House defending its handling of the issue. In a blow to the Libyan government's hope of asserting its authority after the 2011 war that ousted Muammar Gaddafi, the French embassy bombing, was the first of its kind in Tripoli. Both France and Libya called the attack a "terrorist act," "Given the events in Benghazi in the last year, it may not be that surprising that even areas where there is more state control are not immune," a Western diplomatic source in Tripoli said. People can't just point to the east now. In the capital, the presence of state security forces is more evident than elsewhere - pick-up trucks bristling with weapons protect ministries or stand guard at roundabouts. But the city of around 1.7 million people is not immune to violence - gunfire still often rings late into the night as armed brigades fight pitched battles against rival groups. In the last month, the justice ministry was stormed by angry militiamen, the prime minister's aide was abducted and a car carrying the head of the national assembly was shot at. Foreigners have been targeted in everyday crime - car jackings and theft - but the city has been seen as relatively safe compared to the rest of the North African country. "Security in Libya is related to the post-revolution status and the fact that the ministries of interior and defense are being rebuilt," said Nizar Kawan, a national assembly member. The balance of power is not yet on the state's side even though it should have overall power in the country. There has been no claim of responsibility for the bombing but al Qaeda's north African arm, AQIM, threatened retaliation for the French intervention in Mali as recently as last week. Westerners in the region have been on alert since January's bloody hostage-taking at the In Amenas gas plant in Algeria. Officials said it was too early to say who was responsible. In Benghazi, British, Italian, United Nations and Red Cross missions have already been the targets of violence. U.S. officials say militants with ties to al Qaeda affiliates were most likely involved in the September 11 Benghazi attack. "We cannot definitely say this attack was linked to what happened in Benghazi," Interior Minister Ashour Shuail told reporters. The problem is not just the security of embassies but the security of the whole nation. Previous incidents in Tripoli have been minor compared to Tuesday's. In June, a small bomb exploded outside the consulate of neighboring Tunisia; in January, a bomb was thrown at an empty building which U.N. officials had considered using. " (The attack) signals that what in the past was perceived of as some isolated groups operating in the east, in reality are probably a broader network that has links across the country," Claudia Gazzini of International Crisis Group said. Maybe in the east it's easier to operate and carry out such attacks; in Tripoli there is a higher number of government security forces but that doesn't necessarily imply that there is control over the capital. Prime Minister Ali Zeidan's government has sought to clamp down on armed groups, with an Operation Tripoli campaign aimed at dislodging militias from public buildings. But it has faced resistance and still only commands few disciplined police or military officers, often outmatched by thousands of militiamen. There is no security at night, we see no police patrols. We want respect from the state," said Abdelhakim Mohammed of the Supreme Security Committee - a grouping of ex-rebel fighters, now better armed and powerful than the police. Ministers keeping call us militias to discredit us. Analysts say various groups could see gain from attacking French interests in Libya, but they also point to the power struggle between the Libyan authorities and militias. "The French embassy bombing may have been part of a militia turf war," said Geoff Porter, director of North Africa Risk Consulting. A signal to Zeidan that he should steer clear of the more powerful and well-established Tripoli militias and perhaps Operation Tripoli would be best left to peter out. Diplomatic missions are now likely to step up security in light of the attack, which may also deter wary investors. "The exposure of the capital's vulnerability to terrorist attack will come as a severe blow to the Libyan government's faltering efforts to restore investor confidence in the country," IHS Country Analyst Richard Cochrane said.