Saudi Arabia's Grand Mufti, the highest religious authority in the country, has condemned suicide bombings as grave crimes, reiterating his stance in unusually strong language.

The Saudi cleric, whose views influence those Muslims who adhere to the kingdom's hardline version of Islam, denounced suicide attacks after al-Qaeda's 2001 assault on US cities, but his latest comments, published on Thursday, recast the message in sharp terms.

"Killing oneself is a grave crime and a grave sin," Sheikh Abdulaziz al-Sheikh was quoted as saying by the Saudi-owned Al-Hayat newspaper.

"Those who kill themselves with explosives are criminals who are hastening their way to hell."

Nearly two months ago, the mufti, who is appointed and paid by the Saudi government, urged Saudis not to travel to Syria to join Sunni Muslim rebels battling to unseat President Bashar al-Assad.

Riyadh broadly backs the rebels, but with the rise of factions in Syria that claim to be Islam-oriented, the country has grown increasingly worried that Saudis who fight for the anti-Assad cause might one day return home with the aim to unseat the kingdom's government.

The mufti did not refer to suicide bombings in a specific country. Such attacks have most frequently occured in Iraq, Afghanistan and Pakistan lately.