Eight Taliban suicide bombers reportedly struck Jalalabad, Afghanistan's biggest city, in a three-hour attack that coincided with a visit by US Secretary of State John Kerry.
The pre-dawn attack on a police compound killed at least five officers, Voice of America reported, with one of the attackers setting off a car bomb.
Reuters quoted provincial police chief Amin Sharif as saying:
"Three suicide bombers triggered their explosive vests and five were shot dead."
The car bomb was detonated at the entrance of the Afghan National Police compound to allow the other attackers to storm inside.
The attackers were armed with rocket-propelled grenades and light machine guns, Amin said, forcing Afghan security forces into a gun battle.
The London Telegraph cited Taliban militants as claiming responsibility for the attack but claiming that it had targeted "foreigners and Israeli teachers" training Afghan police.
According to the Los Angeles Times, Kerry flew Afghanistan despite Afghan President Hamid Karzai infuriating Washington earlier this month by accusing the United States of colluding with the Taliban.
Kerry has already met with Karzai twice since arriving in Afghanistan on Monday and is also expected to meet with Afghan leaders to discuss the US disengagement from the country over the coming months.
Most foreign troops are due to leave Afghanistan by the end of 2014.