Former Irish Prime Minister Bertie Ahern has said dissident Republican groups in Northern Ireland must not be underestimated.Ahern’s warning came after the second deadly attack on security forces in the province in recent days. Speaking in Dublin, he underlined the need for leaders in both the north and south of Ireland to unite. ‘‘These are a dangerous group and not to be underestimated, and obviously I just lend my voice, like everybody else’s that this really requires both north and south, cooperation between the Gardai and the security forces, which I know is happening, but also for anybody that can help because as long as these people are at bay they’re a danger to this society,’‘ said Ahern. With worries the province could slide back into sectarian violence, Northern Ireland’s political leaders and former enemies have rallied to condemn the recent attacks. Northern Ireland’s Deputy First Minister Martin McGuiness said: ‘‘One thing is absolutely certain and that is the peace process will continue. Why will it continue? It will continue because it has the overwhelming support of the people of this country.” Two men, aged 17 and 37, have been arrested in connection with the shooting of a policeman on Monday. The Continuity IRA says it carried out that killing after another splinter group the Real IRA shot dead two British soldiers at an army base on Saturday.