Nigerian militants attacked villagers and paramilitary forces in neighboring Chad on Friday, killing at least six people in a clash that appeared to be revenge for Chad sending combat troops to fight the Islamic insurgency.

The Boko Haram insurgents were said to have arrived in the early hours of Friday as part of a group of thousands of Nigerian refugees flocking to Ngouboua, a village located north of the capital, Ndjamena, according to military officials and civilians who spoke to The Wall Street Journal.

The gunmen killed six people--five civilians and a paramilitary officer. They also wounded three other officers while four members of Boko Haram were reportedly killed.

"They sneaked in the night...with guns and machetes, killing several people including our village chief," said Issa Mahamat, who confirmed having seen about 10 victims.

The attack shows the widening scope of a conflict that has engulfed Northeast Nigeria, prompting the government to postpone a presidential election for six weeks.

The raid appears to mark a first attack on Chad, which is the latest of Nigeria's neighbors to be targeted by the jihadist group following cross-border raids against Cameroon and Niger.

"This is the first time Boko Haram is attacking us," said Chad's military spokesman Col. Azem Bermandoa Agouna. "The assailants immediately fled into Nigeria when our troops intercepted them."

Chadian troops have killed at least 500 Boko Haram militants since Chad joined its neighbors to fight the jihadist group, according to Col. Azem. Boko Haram aims to create an Islamic state within Nigeria, but that campaign has resulted in a brutal and bloody war spilling across borders.

In the past 10 months, about 10,000 people have died in Nigeria's Boko Haram conflict, according to New York'sCouncil on Foreign Relations. Some 1.5 million have been displaced.

Chad, Nigeria, Cameroon and Niger--neighbors facing Boko Haram threats--agreed last week in the Cameroonian capital Yaoundé to rally a joint force of 8,700 troops to collectively fight the insurgency.

Chad's military is reputed to be a fierce and seasoned fighting force. It helped defeat al Qaeda-backed militants in Mali and has fought in the Central African Republic as well.

In mid-January, Chad's President Idriss Déby Itno deployed 2,500 troops to Nigeria and Cameroon to fight the militants. Cameroon's President Paul Biya had asked for international support to combat the insurgency. "We're not out to force Boko Haram to recoil," said Col. Azem. "Our mission is to eradicate its existence."