Saudi security forces have detained militants suspected of involvement in the bombing that killed at least 18 people in a housing compound in the capital Riyadh at the weekend, a diplomat said on Tuesday. ‘‘A group of suspects in the bombing was detained. The campaign to chase the culprits started immediately after the bombing. Some were also detained and released after interrogation,’’ the diplomat close to the investigation said. The arrests took place in Riyadh and the outskirts. ‘‘The campaign to hunt down those responsible is continuing,’’ the source said. Saudi-born Osama bin Laden’s Al Qaeda network is suspected of staging Sunday’s suicide attack that also wounded 120. Saudi Arabia’s King Fahd vowed on Monday that his country would strike with an ‘‘iron fist’’ against militants. The warning came as a senior United States official said the Al Qaeda network was trying to topple the Saudi ruling family.
