KUWAIT CITY (AFP) - Kuwait will hold a mass funeral on Saturday for 26 victims of a Shi'ite mosque bombing claimed by the Islamic State jihadist group as the shocked oil-rich emirate tightens security.

The interior ministry said in a statement early Saturday that 26 people and the suicide bomber were killed and 227 others were wounded in one of the country's worst bombings and its first ever on a mosque.

The attack targeted Al-Imam Al-Sadeq mosque in the capital Kuwait City during Friday noon prayers.

The mosque authorities said in a statement that "Kuwait martyrs" will be laid to rest at the Shi'ite cemetery, west of the capital, at 4:00 pm (9:00pm Singapore time).

It said that condolences would be accepted for three days starting on Saturday at the Grand Mosque, the largest place of worship for Sunni Muslims, in a show of solidarity.

Kuwait's emir, the government, parliament and political groups and clerics have said the attack was aimed at stirring sectarian strife in the emirate.

Sunni religious and political groups were quick to condemn the attack carried out by the Islamic State, a radical Sunni group which considers Shi'ites to be heretics.

Shi'ites form a third of Kuwait's 1.3 million native population.

The interior ministry has said an unspecified number of suspects were held for questioning in connection with the attack that shook the small Gulf state. No details were provided.

- Day of mourning -

The cabinet announced after an emergency meeting on Friday that all security agencies and police had been placed on alert to confront what it called "black terror".

It also declared Saturday a day of mourning.

Shi'ite activist Abdulwahed Khalfan told AFP that security at Shi'ite mosques was beefed up and citizens' committees have been formed.

The IS-affiliated group in Saudi Arabia, calling itself Najd Province, said militant Abu Suleiman al-Muwahhid bombed the mosque, which it claimed was spreading Shi'ite teachings among Sunni Muslims.

The emir, Sheikh Sabah al-Ahmad al-Sabah, who visited the site immediately after the bombing, said that the "criminal attack is a desperate and evil attempt targeting Kuwait's national unity".

Several countries and organisations including the United Nations, the United States deplored the bombing.

Kuwaiti newspapers said the attack aimed to undermine national unity by fanning sectarian tensions.

"It is a black day ... in which Kuwait woke up to a spiteful bombing that aimed foremost to undermine its national unity and social structure," said Al-Qabas in a front-page editorial.

Al-Anbaa newspaper agreed that the aim of the bomber was to divide society.

"The message of the despicable terrorist who blew himself up is clear: an attempt to ignite hateful strife between the Kuwaiti people," said the daily.

- 'Maximum security' -

Parliament and the cabinet are scheduled to hold a joint meeting Saturday to discuss the consequences of the bombing.

Eight Islamist, liberal and Shi'ite political groups condemned the attack in a joint statement and called on the government to confront extremists.

National oil conglomerate Kuwait Petroleum Corp. (KPC) said Saturday it had raised security at oil facilities to maximum level.

KPC spokesman Sheikh Talal Khaled Al-Sabah said in a statement that all refineries, oilfields and oil sector operations had been placed under heightened security to maintain normal operations.

Oil is Kuwait's main source of income accounting for around 90 percent of public revenues.

The OPEC member says it sits on around 10 per cent of global reserves and pumps around 2.8 million barrels of oil per day.