Police probe mystery explosion
Security forces are investigating whether a loud explosion in Londonderry was linked to a possible attack on police.
Officers trying to detect the cause of the blast have evacuated part of the Waterside area of the city.
Police in Derry said they have received a number of reports of possible causes of the explosion which was heard at around 5pm on Tuesday.
But while the source of the blast has yet to be identified, it is understood that an attack on police is one line of inquiry.
Officers warned members of the public to be vigilant and to report any suspicious objects to police.
"To investigate the circumstances surrounding the explosion, police are evacuating the area around Spencer Road," they said.
It is believed that the areas will be closed until sometime on Wednesday to allow for daylight searches.
A hall is being made available for evacuated residents.
Police said they were grateful to the local community for their patience while the investigation continues.