**Shots have been heard outside a house being surrounded by US police hunting the suspected killer of four fellow officers in Washington State.**Acting on a tip-off, they sealed off an area in Leschi neighbourhood in the city of Seattle and armed Swat team members ringed the property.
Police used a loudspeaker to call on Maurice Clemmons, 37, to come out.
Mr Clemmons has not been named as a formal suspect. There is no confirmation that he is in the house.
News of the siege broke in the early hours of Monday, local time. Washington State is eight hours behind GMT.
The four police officers were shot dead in a single attack at a coffee shop in Parkland, 40 miles (65km) south of Seattle on Sunday morning.
The three male officers and their female colleague had been working on their laptops in the coffee shop when at least one gunman entered.
A sheriff’s spokesman likened the attack to an execution. Other people in the cafe at the time were not injured.