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Four men were killed Sunday as they attacked a Saudi security services base in a "conservative" town north of Riyadh, pro-government media reported.

The attack targeted state security forces in the town of Zulfi, 260 kilometres north of the capital, London-based Arabic daily Asharq al-Awsat reported. 

It said the attackers had rammed a vehicle into a security barrier around the base in an attempt to gain entry.

Two gunmen then stepped out of the vehicle and opened fire, sparking a gun battle with police, who killed them, the paper reported.

A third attempted to flee but was also gunned down, while a fourth died as he tried to set off an explosive belt.

It did not mention any casualties among security personnel.

The Saudi-owned satellite channel Al-Arabiya also reported four people died during an attack, but did not give details.

On 7 April, two men armed with explosives were killed and two others arrested as they attacked a security checkpoint in a predominantly Shia region in eastern Saudi Arabia, which has seen years of demonstrations against the regime.

Sunday's attack took place in a majority Sunni region.

An estimated 10-15 percent of the ultra-conservative kingdom's 32 million population are Shia, although no official figures exist.