Intelligence bosses said that Kenyan youth who had joined Al-Shabaab were fleeing the militant group's strongholds in South Central Somalia to escape ferocious onslaught by regional armies.

The Inspector General of Police, Joseph Boinnet in early June said Al-Shabaab was planning attacks during the holy month of Ramadan in several parts of the country.

The police boss singled out northern Kenya, the coast region and Nairobi as areas vulnerable for attack by Al-Shabaab returnees.

Despite heightened vigilance, Al-Shabaab has in the last few days staged daring attacks in northern Kenya using explosive devices.

Four charity workers died on Tuesday when their vehicle hit an explosive device in Garissa County just a few days after three administration police officers were killed in similar circumstances.

Northeastern Regional Coordinator, Mohamud Saleh early this week maintained that Al-Shabaab was coordinating with local sympathizers to carry out attacks on civilians and security officers.

Werunga said the latest attacks by Al-Shabaab fighters serve as a wake-up call for the government and its bilateral partners to retool the national counter-terrorism strategy.

"What we are witnessing now is a low level insurgency and there is no denying that Al-Shabaab have capacity to either develop or acquire explosive devices to sustain their onslaught across the border," said Werunga.

He added the main aim of the Al-Qaida linked militant group is to demoralize Kenya's security forces by staging covert attacks using landmines and other improvised explosive devices.

Kenya must brace for the new face of terror that borders on random but swift attacks targeting security officers and high profile citizens.

Werunga clarified that Al-Shabaab has the capacity to stage low key attacks despite losing majority of its senior commanders and foot soldiers in the ongoing military operation.

"It is evident we are entering a new phase of insurgency and must therefore enhance our deterrence measures that include better intelligence collection and sharing to minimize new attacks," Werunga told Xinhua.

Kenyan officials have put a brave face despite a series of attacks by Al-Shabaab militants which have claimed dozens of civilians and security agents.

Cabinet Secretary for Internal Security, Joseph Nkaisserry on Tuesday told a parliamentary security committee that Kenya had invested in soft and hard power to defeat terrorism.

He at the same time defended the acquisition of costly military hardware like the Armored Personnel Carrier (APC) to fight terrorism along the Somalia border.

Security experts were emphatic that Kenya requires sophisticated surveillance and intelligence gathering infrastructure alongside community policing to nip terrorism in the bud.

Richard Tuta, a Nairobi based homeland security expert said that a revamped counter-terrorism strategy was urgently required to foil Al-Shabaab's macabre plots.

"We need to evaluate our counter-terror strategies as the threat evolves rapidly," Tuta remarked, adding that better intelligence and use of drones can be effective in eliminating terror masterminds.