London, Dhu-AlQa'dah 25, 1436, Sep 9, 2015, SPA -- British Prime Minister David Cameron on Wednesday appealed to political parties in Northern Ireland to stick to the "noble principles" of a power-sharing agreement and resolve a crisis that threatens to undermine the deal, dpa reported. The crisis worsened on Wednesday after police said a well-known member of Irish nationalist party Sinn Fein was among three Irish Republic Army-linked suspects detained in connection with last month's murder of Kevin McGuigan, a former IRA hitman. Democratic Unionist Party leader Peter Robinson, who heads Northern Ireland's devolved government, threatened to resign on Wednesday unless the regional assembly is suspended pending an investigation of the continuing existence of the IRA and its links to Sinn Fein. -- SPA 19:39 LOCAL TIME 16:39 GMT www.spa.gov.sa/w