Police are dealing with two security alerts in Londonderry on Monday.
Vehicles were hijacked by masked men in the Circular Road and Southway areas of the city within a space of around two hours.
The incidents come on the back of a car bomb attack outside Bishop Street Courthouse over the weekend, and have caused significant disruption in the city.
The first incident happened just before 11.30am, when three masked men hijacked a Transit van at Circular Road.
Police said they threw an object in the back of the vehicle before abandoning it.
A number of homes were evacuated in the area and a community centre at Central Drive in the Creggan was made available.
The Army later carried out a controlled explosion.
A spokesperson for the PSNI said: "A number of homes remain evacuated and the cordons are still in place whilst our investigation continues.
"We continue to ask the public for their patience, and thank them for their co-operation while we work to make both areas safe."
In the second incident, at about 1.45pm, four masked men hijacked a delivery driver's vehicle in Southway.
One of the men reportedly had a gun.
The two people in the van were ordered to drive it to Lonemoor Road and leave it there, police said.
"We are in the process of implementing a public safety operation, establishing cordons and evacuating a number of homes," a spokesperson added.
"Sadly, within two hours today, we are dealing with a second security alert in the City, which means even more disruption for the local community.
"I know this second security alert and the measures we are taking to keep people safe will cause significant inconvenience for the local community, but we have no choice.
"I want to ask the public for their patience, and thank them for their co-operation while we work to make the scene safe."