Man dies after US immigration jail attack

A man armed with a rifle has thrown incendiary devices at an immigration jail in Washington state, and was then found dead after police opened fire, authorities say.

Tacoma police say the officers responded at about 4am on Saturday to the privately-run Homeland Security facility that holds migrants pending deportation proceedings.

The centre has also held immigration-seeking parents separated from their children under President Donald Trump's efforts to deter illegal immigration.

The shooting took place about six hours after a peaceful rally in front of the detention centre, police spokeswoman Loretta Cool said.

She said another rally was planned for later Saturday, but it would have to be held in a different area because of the investigation into the shooting.

Police said the man caused a vehicle to catch fire and that he attempted to ignite a propane tank to set buildings on fire. Police said that besides the rifle, he had a satchel and flares.

Police said officers called out to the man, and shots were fired.

Cool said all four officers fired their weapons, but she didn't have specific details of what took place.

She said the officers weren't wearing body cameras, but the area is covered by surveillance cameras from the detention centre. She said she didn't know if the man fired at the officers.

After the gunfire, officers took cover, contained the area and set up medical aid a short distance away, police said.

Officers then located the man and determined he had been shot and was dead at the scene. His name hasn't been released. No law enforcement officers were injured.

The four Tacoma police officers who fired their weapons have been placed on paid administrative leave as is standard in officer-involved shootings.

A motive for the man's actions has not been determined.