On 6 September, a crude bomb was hurled at a BJP office in Thiruvananthapuram in Kerala, with the party alleging that CPI(M) workers were behind the attack.
No one was injured in the incident, the police said.
The incident occurred around midnight on 6 September, shortly after BJP state president Kummanam Rajasekharan left office for Kozhikode, where preparations are underway for the three-day National Executive and Council meeting from 23 September, which is being attended by senior party leaders and Prime Minister Narendra Modi, party sources said.
At least four workers were on the top floor of the building, housing the office, when the bomb was hurled.
Though no one was injured, glass panes of the main entrance door were damaged in the incident, Thiruvananthapuram City Police Commissioner S Sparjan Kumar told PTI.
The incident comes close on the heels of a series of sporadic clashes between CPI(M) and BJP workers in the past few months in northern Kannur district.
Rajasekharan alleged that CPI(M), the lead partner of the ruling LDF in Kerala, had taken the law into its hands and the police was a "mere spectator".
"Violence of the CPI(M) is increasing each day. A BJP activist was hacked to death in Kannur recently and CPI(M) is behind it," he told reporters at Kozhikode.
"Despite so many incidents, CPI(M) leaders and Chief Minister Pinarayi Vijayan, who is also holding the Home portfolio, have not condemned the series of attacks against BJP and its workers," he said.
BJP leaders PK Krishnadas and MT Ramesh slammed the CPI(M), saying the bomb attack against the party office should not be seen as an "isolated" incident.
"This is a calculated and well-planned attack against the BJP and the CPI(M) is behind it," they said. All flex boards in front of the office were also destroyed, Krishnadas said.
Television channels aired a CCTV video footage showing a man riding a motorcycle minutes before the blast and the police are on the lookout for him.