KABUL, Afghanistan - A suicide bomber killed six people and wounded more than 30 during rush hour in the Afghan capital on Wednesday, striking near the presidential palace and the Finance Ministry, officials said.

The blast was the second attack in a week in Kabul, suggesting that Afghanistan's insurgency is revving up as the customary winter lull in the fighting approaches an end.

Last week, the Taliban asserted responsibility for a suicide bombing in the capital that killed a powerful regional police commander.

Afghan officials said the suicide bomber on Wednesday was apparently in a vehicle packed with explosives and struck in the heart of Kabul, in front of the Finance Ministry and near a police station. The target of the attack remained unclear, the officials said.

As of Wednesday evening, no one had claimed responsibility for the blast.

The attack occurred a day after President Obama said he would slow the planned withdrawal of 9,800 U.S. troops from Afghanistan, freezing their levels through the end of the year.

The decision came after a meeting with Afghan President Ashraf Ghani, who was on his first official visit to Washington since taking office six months ago.

Before his departure to the United States, Ghani told reporters that the government and the security forces were bracing for the Taliban's annual spring offensive. The government, he said, was expecting "a difficult spring."