Nigeria Gas Company spokesman Violin Antaih said on Tuesday that suspected oil militants attacked a gas pipeline in Nigeria’s restive south, breaking a fragile truce between them and the government, The Guardian reports.

The attack on a pipeline operated by the Nigerian Gas Company Limited, a subsidiary of the Nigerian National Petroleum Corporation (NNPC), took place on Saturday near Sanomi creek, close to the oil hub of Warri in Delta state.

The attack is the first on Nigeria’s oil and gas infrastructure in months and takes place amid ongoing negotiations between Niger Delta leaders and President Muhammadu Buhari’s government.

In a cryptic tweet on Tuesday morning, the spokesman of main rebel group the Niger Delta Avengers wrote “la vittoria è nostra” (Italian for “victory is ours”). The Nigerian military said it was investigating the incident.