Manchester attack appalling and senseless, says Jones
First Minister Carwyn Jones has condemned the "appalling and senseless" Manchester suicide attack.
An explosion left 22 people dead and dozens injured following a pop concert by US singer Ariana Grande on Monday night.
AMs held a minute's silence in the Senedd chamber as a mark of respect.
Political campaigning for the general election has been suspended, and a vigil was held on the steps of the Senedd in Cardiff Bay.
All Welsh party leaders have expressed their thoughts for the victims of the attack.
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At the start of Tuesday's business in the Senedd, First Minister Carwyn Jones told the chamber: "This was a particular form of cruelty at work because this act was directed at teenagers coming out of a concert.
"It's difficult to imagine an act more appalling and more senseless."
Mr Jones said he received a national security briefing from the Cabinet Office by phone on Tuesday morning.
"The message from this chamber is that we will not be cowed, nor will we shrink into the shadows, nor will we change our way of life," he said.
During First Minister's Questions Mr Jones said security arrangements for the forthcoming Champions League Final in Cardiff on 3 June were "robust".
But he added: "What I can say to people is that of course we will be taking further advice with regard to the Champions League, but a lot of the work has already been done regarding security."
Presiding Officer Elin Jones, on behalf of all members of the assembly, expressed their "heartfelt condolences".
"I know people the length and breadth of Wales in all communities will condemn this unforgiveable act of violence, and will provide all possible support to the authorities and people of Manchester as they come to terms with what has happened," she added.
In an earlier statement, Welsh Conservative leader Andrew RT Davies said: "Targeting a concert with so many children and families is the ultimate act of cowardice and as a country we will come together to show those who commit such atrocities will never, ever win."
Plaid Cymru leader Leanne Wood said: "The thoughts and sympathies of all of us in Plaid Cymru go out to all the people affected by last night's horrific events in Manchester."
UKIP's leader in the Welsh Assembly, Neil Hamilton, said: "Terrorists will never win", adding "our victory will be the final one because our democratic institutions will not be destroyed, inhibited or undermined".
Welsh Liberal Democrat leader Mark Williams said: "I am deeply shocked & saddened by events that took place in Manchester yesterday evening. Our thoughts & prayers are with all those affected."
The Wales Green Party had been due to launch its election campaign in Cardiff on Tuesday, but has postponed it due to events in Manchester.
Leader Grenville Ham said: "This transcends politics.
"My thoughts are with the families and friends of the victims of the attack and the community in Manchester."