A day after a gang war involving machetes and a country bomb in Chintadripet, the police have arrested four people under the Explosives Act.

According to reports, Malarvizhi (50) and her son Azhaguraja (31) are lawyers and were returning after appearing in a case at Egmore court on Thursday with Vijaykumar and Manikandan. They were travelling in an auto when the incident happened.

Around 12.30 pm on Thursday, as the auto reached Casino theatre, an eight-member gang, suspected to be the accomplices of history-sheeter Sivakumar, intercepted the vehicle and attacked Malarvizhi, who got injured on her head and hand. As the duo attempted to run towards the Dams road adjacent to Anna Salai, Azhaguraja, who was also injured in the attack, retaliated by hurling a country bomb at the gang. Police rushed to the spot and immediately took Malarvizhi to the Government Stanley Medical College and Hospital for treatment.

Police suspect a history of enmity between the two gangs to be the reason for the attack on Friday. Malarvizhi’s husband Sekar was an accused in the murder of Sivakumar’s brother in 2001. In retaliation, Sekar was killed the same year. Sivakumar’s gang also eliminated Sekar’s cousin in 2003.

The incident on Thursday caused a flutter among the police as it came a day before Chinese President Xi Jinping was expected to arrive in Chennai for a bilateral meet with Prime Minister Narendra Modi, and security was being beefed up at multiple levels across the city to ensure the meeting goes off smoothly.

Police arrested Malarvizhi, Azhaguraja and the two men who were with them on Friday and booked them under the Explosives Act for possessing a country bomb. The police had nabbed two men -- Aravind and Appun -- from the gang on Thursday after the attack.