2 police officers killed in Iowa 'ambush'

Two police officers in the US state of Iowa were shot dead in separate attacks on Wednesday, with both "ambushed" as they sat in their cars, authorities said.

"It doesn't look like there was any interaction between these officers, and whoever the coward is... shot them as they sat in their cars," Des Moines Police Sergeant Paul Parizek said in an early morning news conference.

"It looks just like that, that these officers were ambushed."

The first officer was found dead just after 1:00 am (0600 GMT) in Urbandale, a suburb of the state capital Des Moines.

The second officer was found shot about 20 to 30 minutes later in Des Moines proper and died after being taken to the hospital, according to US media.

Parizek said officers would be doubling up to patrol in pairs in the wake of the shootings.

"There is a clear and present danger to police officers right now and we've doubled up our police officers" so that no one is working alone," he said.

He added that police had no information on how many suspects were involved or who they were, The Des Moines Register said.

The two officers are the first to be shot in the line of duty Des Moines since 1977, when two officers were gunned down, the paper said.

The United States was on edge for weeks in July following the shootings in Dallas of five officers and a similar assault in Baton Rouge, Louisiana, where three officers were shot dead by a former military veteran.