Afghan security forces, along with US and Nato-led troops, are struggling to tackle resurgent Taliban fighters who have stepped up suicide attacks and roadside bombings across the country.
Al Jazeera's Teresa Bo, reporting from Kabul, said the police were an easy target for the Taliban, and that Uruzgan was a centre for the group.
"They are not as well equipped as the foreign troops here, so they are chosen repeatedly for attacks like this one," she said.
"This is an attempt by the Taliban to destabilise the situation, to make a claim that they have control over some specific areas around the country.
"This is one of the main reasons why the independent electoral commission here has postponed the elections until August 20."
In 2008, nearly 870 police officers died in attacks by anti-government fighters, according to a tally of figures collected by The Associated Press news agency.
During the past three years the Taliban have gained greater control of large swathes of the south of the country, following their initial defeat after a US invasion in 2001.