Mozambique President Filipe Nyusi. (AP Photo/Tsvangirayi Mukwazhi)

Mozambique's president announced Monday several arrests following a wave of deadly attacks blamed on jihadists.

In his first comments on the violence engulfing the northeastern Cabo Delgado region, President Filipe Nyusi vowed that security forces would be "firm and ruthless" in pursuing the shadowy group blamed for more than 30 deaths.

Vast riches of natural gas were recently discovered off the region's coast but the violence has thrown the viability of exploiting the reserves into doubt.

"We condemn these acts and will not rest until their perpetrators and collaborators are neutralised and held accountable for their crimes," said Nyusi as he marked Mozambique's 43rd year of independence at a media conference in Maputo.

"Our defence and security forces are on the ground -- firm and ruthless."

Moscow and Washington said earliler this year they were available to help Maputo solve the attacks.

The president also revealed that several suspects, male and female, Mozambican and foreign, had been arrested over the bloodshed but did not give details.

There have been more than 10 attacks on villages in northeast Mozambique since October, featuring beheadings and arson.

Thousands of soldiers and police have been deployed to Cabo Delgado to confront the wave of attacks but the violence has continued unabated.

Since the first attack in October there have been reports of hundreds of arrests -- as well as extra-judicial killings.

Nyusi called for calm and warned that the attackers were seeking to "demoralise our will to exist as a nation, as a an organised society".

"We must never allow anyone --  whether they are Mozambican or foreign, to spread violence in the country. We have built peace stone-by-stone."