Thousands of people have gathered in Omagh to mark the death of Northern Ireland police officer Ronan Kerr.
The organisers have said they want to send a message to those who want to return NI to a violent past.
Those attending, including family and friends of Constable Kerr, held a minute's silence in his memory.
The 25-year-old Catholic officer died when a booby-trap car bomb exploded outside his home in the town last Saturday.
Sinead O'Kane, Ronan Kerr's cousin, attended the rally. She said she wanted dissident republicans to end their campaign.
She added: "It has to stop now, and let his death not have been in vain. And hopefully the people who are out there will be listening and it will strike a chord with someone and they'll come forward and help in the murder investigation."
Organiser Gareth McElduff used Facebook to gain support for the rally.
He said: "Everybody seems happy to come out today to show their support, first of all for the Kerr family and to show overall their support for the peace process.
"And although these are major, major setbacks in the peace process, hopefully the amount of people that is going to come out today is going to show everybody that we want peace in Ireland again and we don't want to go back to the Troubles."
Recent bombings and attempted attacks have been widely condemned in Northern Ireland.
The discovery of a 500lb bomb in Newry on Thursday has reinforced police claims that the condemnations have had no effect on the dissidents responsible.
PSNI Ch Supt Alasdair Robinson said the Newry device was "sophisticated and substantial", and could have caused huge devastation and loss of life.
The bomb was stored inside a wheelie bin in a van under the main Belfast to Dublin road.
Police believe the van was abandoned in the underpass because of increased police activity following the murder of Constable Kerr.
In the wake of the find, politicians have said they feared the device could have caused similar devastation to the Omagh bomb which killed 29 people, including the mother of unborn twins, in 1998.