Air force jets attacked a rebel intelligence base deep in northern Sri Lanka early Wednesday, stepping up a punishing wave of air strikes a day after Tamil Tiger fighters launched a surprise attack on a military base, the military said. The Tamil Tigers said the bombs hit a civilian settlement in the rebel's administrative capital of Kilinochchi, destroying 12 houses. Separate battles between the two sides killed 19 rebels and two soldiers, the military said. The air force has conducted a series of bombing raids over rebel-held territory in the north since the Tamil Tigers attacked a military complex in Vavuniya early Tuesday with a massive artillery barrage, aerial bombing and a ground assault conducted by suicide attackers.