The death toll from a suicide attack on a Shia mosque during Friday prayers in the Kuwaiti capital has risen to at least 25, the interior ministry says.

Another 202 people were wounded, it added. Images circulating online show bodies on the mosque floor amid debris.

The blast hit the Imam Sadiq Mosque in a busy area to the east of Kuwait City.

An Islamic State- (IS) affiliated group said it was behind the attack. IS has carried out similar recent attacks in neighbouring Saudi Arabia and Yemen.

However, this is the first attack on a Shia mosque to take place in the small Gulf state.

An Islamic State-affiliated group said it was behind the bombing. Photo: AFP

A Kuwaiti MP, who saw the attacker, said the mosque was packed with some 2,000 people when there was a loud explosion, Reuters reported.

"It was obvious from the suicide bomber's body that he was young. He walked into the prayer hall during sujood [kneeling in prayer], he looked... in his 20s, I saw him with my own eyes," Khalil al-Salih told the news agency.

A paramedic, speaking to AP news agency, said most of the victims men and boys attending Friday prayers.

Footage said to be taken in the aftermath of the blast showed dozens of men in blood-splattered white robes spilling out of the smoke-filled mosque into the street outside.

Kuwaiti Prime Minister Sheikh Jaber al-Mubarak al-Sabah said the attack was an attempt to threaten national unity. "But this is too difficult for them and we are much stronger than that," he added.

State TV showed the Kuwaiti Emir, Sheikh Sabah al-Ahmad al-Sabah, visiting the damaged mosque.

An IS affiliate calling itself the Najd Province - the same group that claimed a pair of bombing attacks on Shia mosques in Saudi Arabia in recent weeks - said it was behind the attack.

A spokesman for Islamic State this week urged the militant group's followers to step up attacks during the Islamic month of Ramadan.

Sunni-ruled Kuwait has a large Shia minority, which IS considers to be heretical.