MANILA (UPDATE) - A leader of a militant group who was directly involved in the kidnap and execution of Canadian and German nationals was among those killed by Philippine troops in Bohol this week, the military said on Wednesday.

Troops killed at least six members of the Islamic State-linked Abu Sayyaf during the firefight on the popular tourist island of Bohol on Tuesday, but suffered four casualties.

The military has recovered the body of Muamar Askali, also known as Abu Rami, a former spokesman for Abu Sayyaf, a group well known for extortion, piracy and kidnaps for ransom.

Armed Forces chief of Staff General Eduardo Año described Abu Rami as "a very notorious Abu Sayyaf leader" responsible for several atrocities.

The group last year beheaded Canadians John Ridsdel and Robert Hall. Elderly German Jurgen Kantner suffered the same fate in February when a $600,000 ransom demand was not paid.

Año said Abu Rami was "trying to make a name of his own" and had risen to become one of Abu Sayyaf's top leaders. He was involved in what the Army said was a thwarted attempt to kidnap tourists in Bohol during Holy Week in the mainly Roman Catholic nation.

Año said the situation in Bohol, far from Abu Sayyaf's island strongholds in the South, was now "back to normal" even as security forces chased down other fighters involved in the gun battle.

At least 3 soldiers, 1 policeman and 6 Abu Sayyaf fighters were killed in the clash.

Capt. Jojo Mascariñas, spokesperson of the Army's 302nd Brigade, identified the casualties from the government's side as 2nd Lieutenant Espelito Saldua, Jr., Corporal Meljun Cajaban, Sergeant John Dexter Duero, and PO2 Rey Anthony Nazareno.

The clash happened after the United States, Canadian, Australian and British embassies warned citizens about kidnappings during the holiday and advised against travel to Central Visayas, which includes Cebu and Bohol.

The military has declared all-out war with Abu Sayyaf on the islands of Jolo and Basilan, but is hamstrung by its presence among large civilian communities.

Abu Sayyaf has its roots in separatism but its activities are mostly banditry and piracy and it has invested the profits of its business in modern weapons and fast boats.

The military has struggled to curb the piracy, with the group's boats difficult to detect when they target slow-moving trawlers.

Indonesian, Malaysian and Vietnamese vessels are frequently targeted and their crew abducted, and the government has sought international help to patrol the Sulu Sea.

The government also says it has credible intelligence that some Abu Sayyaf leaders are in contact with Islamic State with a view to establishing a presence in the mainly Muslim southern Philippines.

• READ: Islamic State pushing for Asian links, expansion, Philippines says

President Rodrigo Duterte has warned of a potential Islamic State "contamination".

-- With reports from Annie Fe Perez and Junrey Nadela, ABS-CBN News; Reuters