At least 30 people died and 42 were injured in a triple suicide attack in a restive area of northeastern Nigeria, officials said on Monday.The attacks were carried out on Sunday evening in Mandarari in Borno, which borders Chad, Niger and Cameroon.Three people -- two women and a man -- carrying homemade explosives blew themselves up at a centre where people had gathered to watch television, the country's State Emergency Management Agency (SEMA) was cited as saying by Efe news.Usman Kachala, SEMA Search and Rescue Operations Director, visited the site of the incident and said that 17 people were killed instantly at the scene.The rest of the victims died later after they did not receive medical treatment because the Army had cordoned off the area, Kachala told reporters.It was not clear who was responsible for the attacks but the state of Borno is frequently targeted by the extremist group Boko Haram, which regularly uses women and men as suicide bombers in a similar manner.Boko Haram has been fighting since 2009 to impose an Islamic state in Nigeria, which is a predominantly Muslim country in the north and mostly Christian in the south.Since then, more than 20,000 people have died and almost two million people have been displaced, according to estimations from the United Nations.A joint multinational force comprising of Nigeria, Niger, Cameroon and Chad has significantly weakened the Boko Haram insurgency, although extremists still launch indiscriminate attacks on sensitive areas such as schools, mosques and markets.