Senior nationalist politicians have said they won't be deterred after security alerts sparked by reports of explosive devices at their offices.
West Belfast MP Paul Maskey was defiant after a bomb alert outside Sinn Fein's constituency offices in west Belfast.
SDLP deputy leader Nichola Mallon MLA also said her party will not be intimidated after reports her North Belfast office had also been targeted.
It was one of three security alerts in the city yesterday.
Secretary of State Brandon Lewis said his thoughts were with both politicians.
"These pathetic attempts at intimidation are totally unacceptable. Nothing can justify such actions against public representatives who willingly serve in the best interests of their communities," he said.
Unionist politicians also condemned the alerts, with UUP MLA Doug Beattie saying it would do nothing to help concerns around the Northern Ireland Protocol.
Sinn Fein was contacted by police yesterday after a report that an explosive device may have been thrown at a party office on the Falls Road.
"This report is very concerning and I condemn those responsible," Mr Maskey said. "They have nothing to offer society and they bring nothing but disruption to the local area.
"This is an attack on the entire community and an attempt to undermine democracy but it will not succeed. Sinn Fein will not be deterred by these types of incidents and will continue to serve the entire community."
PSNI Inspector Peter Brannigan said: "Information was received to suggest devices may have been thrown at an office on Falls Road, Belfast and police are seeking to establish the veracity of this information. The local community is asked to be vigilant and report anything out of the ordinary to police."
Police searched the area around Ms Mallon's office after a report of an explosive device being thrown at it yesterday afternoon.
"I want to make it clear that neither I nor my party will be intimidated or deterred by those responsible. We are committed to representing people in North Belfast and in every community across Northern Ireland," the Minister for Infrastructure said.
Chief Inspector Darren Fox said later that officers checked the area and nothing was found.
UUP leader Steve Aiken condemned the incident as "absolutely despicable intimidation".
"All other political parties should also call out this pathetic attempt to undermine our democracy," he said.
His party colleague Doug Beattie MLA said such incidents would not help with rising tensions around the NI Protocol.
"This won't help anybody. We need to make sure we are trying to deal with the issues, which is the protocol, in a legal manner and this is just unhelpful," he said.
DUP MLA Christopher Stalford said there was "absolutely no place for criminal behaviour like that and anyone who has any information about the identity of those responsible should come forward and share that with the police".
Earlier, a suspicious object which sparked a security alert in the city centre was declared as "nothing untoward".
Council offices on Adelaide Street and Linenhall Street were sealed off at around lunchtime and all employees asked to leave the buildings.