CAIRO  A five-day-old uprising in Libya took control of its second-largest city of Benghazi and spread for the first time to the capital of Tripoli late on Sunday as the heir-apparent son of its strongman, Col. Muammar el-Qaddafi, warned Libyans in a televised speech that their oil-rich country would fall into civil war and even renewed Western “colonization” if they threw off his father’s 40-year-long rule.

In a rambling, disjointed address delivered about 1 a.m. on Monday, the son, Seif al-Islam el-Qaddafi, played down the uprising sweeping the country, which witnesses and rights activists say has left more than 200 people dead and hundreds wounded from gunfire by security forces. He repeated several times that “Libya is not Tunisia or Egypt”  the neighbors to the east and west that both overthrew their veteran autocrats in the space of the last six weeks.

The revolt shaking Libya is the latest and most violent turn in the rebellion across the Arab world that seemed unthinkable just two months ago and now poses the greatest threat in four decades to Colonel Qaddafi’s autocratic power. The United States condemned the Qaddafi government’s lethal use of force.

Witnesses in Tripoli interviewed by telephone on Sunday night said protesters were converging on the capital’s central Green Square and clashing with the heavily armed riot police. Young men armed themselves with chains around their knuckles, steel pipes and machetes. The police had retreated from some neighborhoods, and protesters were seen armed with police batons, helmets and rifles commandeered from riot squads.