An Orange hall and a Sinn Féin constituency office have been extensively damaged in separate fires.
Seagoe Orange hall in Portadown, Co Armagh, was badly damaged in a blaze which the fire service is treating as arson.
Meanwhile a serious fire at an office used by Sinn Féin Fermanagh-South Tyrone MP Michelle Gildernew was described by fire authorities as suspicious.
The fire at the Orange hall was started in the early hours of yesterday after a window was broken.
David Jones, a spokesman for the Orange Order in Portadown and a veteran of the Drumcree church parades since 1995, said he was shocked and surprised by the incident.
He claimed the hall had never been attacked before.
"It caused quite a bit of damage to the interior - windows, banners and chairs were ruined as well."
Referring to efforts to resolve the Drumcree impasse, Mr Jones said: "Very small-minded individuals have taken it upon themselves to raise tensions - it serves no purpose to anyone and it's hard to understand the mindset of anyone who carries out this type of attack."
In Fermanagh, Sinn Féin agriculture minister Ms Gildernew said the fire at her offices in Lisnaskea had done a lot of damage.
Three floors in the four-storey building were extensively damaged in the fire which was reported before 3am yesterday.
The building is also used by victims' campaigners Firinne.
A representative said yesterday its work would continue, with colleagues working from home if necessary.