Gunmen Attack Dallas Police Headquarters
The police headquarters in the US city of Dallas, Texas, has come under attack by an unknown number of gunmen who opened fire on officers.
One suspect fled the scene in what was described as an armoured van and is involved in a standoff in a car park.
A number of bags were found outside the police HQ, at least one of which contained explosives including pipe bombs, police said on Twitter.
The motive for the attack is not clear. No officers have been hurt.
Dallas Police Chief David Brown quoted witnesses as saying that as many as four suspects were involved in the initial shooting at about 00:30 (05:30GMT) on Saturday. However, he said this had not been confirmed.
He said one suspect then fled the scene in the van, ramming a police car.
A police chase involving dozens of squad cars ended in a car park in Hutchins, about nine miles (14km) from central Dallas, and officers are negotiating with the occupant of the van, Mr Brown said.
The van, which has been disabled using a police rifle, appeared to have gun ports built into its sides.
Police said the man had identified himself as James Boulware.
Mr Brown said police could not confirm his identity, but said that officers had attended three incidents of domestic violence involving a man with that name in which he had said he wanted to "blow up" the police because they had taken his child and accused him of being a terrorist.