MAIDUGURI, Nigeria (Reuters) - At least 30 people were killed in a triple suicide attack in northeast Nigerian state of Borno, state emergency officials said on Monday - the biggest mass killing this year by Islamist militants.

No group has yet claimed responsibility for the attack, which prompted President Muhammadu Buhari to call for security to be stepped up in areas where large groups gather.

The Boko Haram group and its Islamic State splinter group have often carried out attacks targeting civilians and the military in Borno state.

Their attacks during a decade-long insurgency have killed more than 30,000 people and displaced millions of civilians.

“Yesterday (Sunday) around 8 p.m. (1900 GMT) it was reported that there was a very loud explosion in (village of) Konduga. On reaching the scene of the incident we found there was a lot of casualties. In fact the death toll was over 30 and the injured over 42,” an emergency service official told Reuters.

Earlier the village head, Bulama Kalli, said three suicide bombers had taken part in the attack, targeting a place where villagers had gathered to watch a soccer match on a large screen. Most of those killed have now been buried while several survivors are still in hospital in Maiduguri, Kalli said.

The military did not respond to a request for comment.

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Boko Haram regards soccer - often watched by Nigerians while drinking beer - as un-Islamic and a demonstration of corrupting Western influence.

Konduga is located some 25 km (15 miles) from Maiduguri, the state capital of Borno state.

Buhari’s spokesman said the president had called for security measures to be put in place at open air screenings.

“He urges security agents to sustain surveillance in all theaters of security challenges in the country, taking into consideration the unconventional methods deployed by terrorists to harm innocent and unsuspecting victims,” spokesman Femi Adesina said in the statement.

Buhari began his second four-year term last month after winning an election in February in which he promised to improve security in Nigeria.

Nigeria’s government says Boko Haram and the rival Islamic State West Africa Province group have been largely defeated - that is, driven out of territory they once held - but they continue to launch attacks on civilian and military targets.

“The Nigerian authorities must do more to protect civilians, especially in areas like Konduga that have frequently been targeted by Boko Haram,” Amnesty International said in a statement.