Nairobi - A court ruled Friday that Kenyan police can continue detaining five people who allegedly planned to attack a Nairobi courthouse so a Muslim cleric facing terror charges could escape.Police accuse the suspects and the cleric of being members of the al-Qaeda-linked al-Shabaab militant group from Somalia that has vowed vengeance on Kenya for sending troops into Somalia to fight the militants.The Anti-Terrorism Police Unit said the suspects plotted to attack the Milimani Laws Courts building in the capital on Feb. 16, when Sheik Guyo Gorsa was expected to appear on terrorism and related charges.Gorsa, a Muslim religious leader, was arrested in January in Marsabit County. After his arrest, local residents destroyed a Roman Catholic church and a bank.The court ruled Friday that the five suspects could be held for another 30 days.Police say the suspects were arrested in mid-February after officers spotted a vehicle loaded with explosives and weapons hidden in a thicket in the county of Isiolo. The report says officers were shot at when they approached the vehicle and they returned fire, killing one suspect.Two other people were arrested at the scene, and authorities say the vehicle was found to be rigged as a bomb with 80kg of TNT. Police also removed five rifles, 36 loaded magazines, 36 unprimed hand grenades and 18 improvised bombs, authorities say.Al-Shabab has vowed to strike at Kenya for deploying troops to Somalia in 2011 to fight the militants, who were threatening to topple Somalia's weak government. The group has claimed responsibility for numerous attacks in Kenya, including the September2013 assault on the Westgate Mall that killed 67 people and the April 2015 attack on Garissa University that caused 150 deaths, the majority of them students.KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook.