Suicide bombers on Tuesday killed at least 19 people and wounded more than 30 others in separate attacks in western and southern Afghanistan, raising fears of a renewed spring offensive by insurgents.

Officials say the first and deadliest attack took place in western Herat province after two suicide bombers, who were being pursued by police, rammed their explosives-laden car into a government compound near the provincial capital, Herat. They said at least one of the bombers was wearing a burqa.

Hours later, at least four policemen were killed when three suicide bombers stormed a police compound in southern Helmand province. Local officials said two of the assailants were able to set off their explosives, while a third was shot dead by police guarding the Musa Qala compound. A police commander was wounded in the attack.

The Associated Press reports that the Taliban has claimed responsibility for both attacks.

Herat province, which borders Iran, is normally relatively peaceful, with most insurgent attacks concentrated in Afghanistan's south and east.

Observers are concerned the Taliban may attempt a repeat of last year's spike in violence during the warmer spring months, which saw several high-profile attacks on Afghan and foreign bases.

NATO troops have already transferred security control of large portions of Afghanistan to local authorities. All foreign combat troops are scheduled to leave the country by the end of 2014.