Youths attacked police after the arrest of a prominent republican
A man and a woman have been arrested over the murder of Northern Ireland constable Stephen Carroll, the Police Service of Northern Ireland said.
Pc Carroll, 48, was shot while on duty in Craigavon, County Armagh, on Monday.
The man, 37, and woman, 30, were arrested in the town in connection with "serious terrorist crime", taking the number of people being held to five.
Meanwhile, police probing the murder of two soldiers have come under petrol bomb attack from rioters in Lurgan.
The officers had been carrying out searches in Lurgan where prominent Republican Colin Duffy was earlier arrested over the killings. He is still being questioned.
Police searched Mr Duffy's house throughout Saturday and came under attack from youths who threw stones at them.
Republican protesters gathered in the early evening threw a number of petrol bombs at the police in several different places in the town.
One police officer was injured after being hit on the arm with a brick.
Also in Lurgan, officers probing the murder of Constable Carroll have found a gun and ammunition.
Along with the two arrests on Saturday over Constable Carroll's killing, a 17-year-old boy and two men remain in custody in connection with the case.
Mr Duffy, 41, is one of four men being quizzed about the soldiers' murders at Massereene Army base.
Detectives investigating the killings also carried out an operation in Bellaghy, County Londonderry.
Roman Catholic, Church of Ireland, Presbyterian and Methodist clergy will hold special services on Sunday where church leaders are asking people to wear purple ribbons in protest at the recent murders.
There will also be prayers for an end to violence.
Sappers Mark Quinsey and Patrick Azimkar were shot outside the base in Antrim. About 500 people attended a vigil at the scene on Saturday.
The gathering, which was organised by Antrim Borough Council, was addressed by the mayor of the town and local clergy. The mayors of Wexford, Cork, Westmeath, and Wicklow also attended.
Dissident Republican group the Real IRA said it carried out the attack.
Mr Duffy is a former IRA member who has been critical of Sinn Fein's support for the police service.
Two other men aged 32 and 21 were arrested over the murders. A fourth man was arrested in the Antrim area on Saturday night.
Sappers Quinsey, 23, from Birmingham, and Azimkar, 21, from Wood Green, north London, were attacked after coming out of the base to collect pizzas they had ordered.
Two gunmen in a car parked nearby opened fire with semi-automatic rifles.
Four other people, including two pizza delivery men, were injured.
The soldiers, from 25 Field Squadron of 38 Engineer Regiment, were murdered just hours before they were to have been deployed in Afghanistan.
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