Kenyan police on Sunday expressed fears that there could be more casualties after Sunday explosion on a bus in a Nairobi residential estate left at least seven people dead and more than 30 others injured.

Kenya Red Cross Society however, confirmed seven deaths and more than 30 injuries. However, regional police commander, Moses Ombati said that from the scene of the incident, they could confirm five fatalities and more than 30 others injured in the explosion at about 4 p.m. local time (1300GMT).

"We are worried the number of casualties could be higher since there were two more vehicles behind after an explosion on a 25- seater mini bus which was blown up by the explosive device," Ombati told journalists at the scene of the incident in Eastleigh.

"Several have been rushed to the hospitals and expect the number of casualties to be higher since there were also some passersby and bystanders who were also hit by shrapnels," Ombati said.

Eye witnesses told Xinhua that the blast was hurled inside the minibus that was ferrying passengers to Route 28 near St. Teresa Church in Eastleigh, largely inhabited by Kenyans of Somali origin (Somalis) which has been dubbed as the "small Mogadishu."

"I was here when the incident took place. There was a KBN saloon car that was trailing the vehicle which was blown up by the blast. The car swiftly overtook the minibus then suddenly a man alighted from the car and boarded the minibus and within a minute alighted and then what followed was a blast," said one of the witnesses who sought anonymity.

"The car which carried the man unfortunately sped up, leaving the suspect behind, forcing some of the passengers and bystanders to chase him where they beat him up. He was arrested and taken to Pangani police station as the first suspect. From the scene I counted eight bodies of the people who died on the spot," the witness told Xinhua at the scene.

He said the unidentified suspect was saved by the police from mob lynching. He said the police were forced to fire in the air to disperse the angry crowd who were baying for his blood.

The regional police chief said the injured have been rushed to the Kenyatta National Hospital for treatment, which has sent out appeal for more blood to help the victims of the grenade attack.

Among those being treated at KNH is the suspect said to have carried out the attack. Other reports indicated there are running battles in Eastleigh area after the grenade attack.

Tension is high in the area as the residents are attacking Somalis whom they suspect to be behind a spate of insecurity that has affected the residential estate in the recent past.

However, Ombati said the security forces have been deployed in Eastleigh to contain the violence and that the police have also launched a major crackdown to apprehend those behind the heinous acts.

"We have deployed more police officers in the estate to help contain violence since we understand there are specific people who are being targeted after the blast," Ombati said.

"We will manage the situation. No more deaths will happen in Eastleigh after this blast. We will manage the situation and we are in control," he vowed, after several people have been rounded up and beaten senselessly by the residents.

Ombati said the incident came as security in key towns in Kenya has been put on a high alert following Kenya's military operations in Somalia which sparked threats from the Al-Shabaab group that it will retaliate deep in Kenya. The trend of the attacks particularly in northern Kenya and Nairobi, which seemingly are well coordinated since few suspects have been arrested, has heightened worries among Kenyans.

He said security has been stepped up and he appealed to city residents to be extra vigilant and take security measures seriously, regardless of their status in society.

The police now believed terror suspects will not operate freely unless permitted by their local host communities and have appealed to the public to report suspicious looking people to them for action.

The police have particularly warned against the laxity in the screening of cars for explosives at all shopping malls and any business or social gatherings with at least 10 people at any given moment that these might be vulnerable to attacks.