At least two children have been killed and two others wounded when a hand grenade was allegedly thrown into a church in the Kenyan capital, Nairobi, police officials say.

Moses Nyakwama, the city's police chief, confirmed the injuries in the attack on Sunday.

He said that police suspected the cause of the explosion was a grenade.

Charles Owino, a deputy police spokesman, said that the attack at St Polycarp's church occurred on Juja Road, in the eastern part of the city.

The grenade exploded, spraying the children with shrapnel.

Blood-stained children's jackets and shoes lay scattered on the floor, surrounded by remnants of metal walls that were broken and twisted by the force of the explosion.

"The children who attend this service are aged between six and 10... we usually divide them according to their ages," said Livingstone Muiruri. "They had just started the morning session when the explosion occurred."

"We were in the main church so we all ran there to assist the kids," he said.

Janet Wanja was just entering the church when the blast shook the building.

"I heard a loud explosion and then heard kids screaming," she said. "I am traumatised by what I saw, kids with injuries and blood all over. "Why are they attacking the church?"

Al-Shabab suspected

"We suspect this blast might have been carried out by sympathisers of al-Shabab," said Owino. "These are the kicks of a dying horse since, of late, Kenyan police have arrested several suspects in connection with grenades."

Police were also investigating the possibility that the blast was a result of a bomb that had been placed in the building earlier, Wilfred Mbithi, another senior police official, told AFP.

Following the attack, dozens of angry young men targeted people of Somali appearance and their homes in the area. Police units were deployed to keep the angry mob from causing damage.

The attack on the church came days after Kenyan troops launched an offensive on the southern Somali port of
Kismayo, the last stronghold of the al-Shabaab, forcing the fighters to flee.

Masked assailants launched simultaneous gun and grenade raids on two churches in the northern town of Garissa in July, killing at least 17 people.

Kenya has suffered a series of grenade attacks since it sent troops across the border last October in pursuit of al-Shabab fighters who it blamed for kidnapping its security personnel and Western tourists.