* President Sharif says move meant to allow people to pray

* Shabaab attacks government-held checkpoint in Mogadishu

By Abdiaziz Hassan and Sahra Abdi NAIROBI, Aug 22 (Reuters) - Somalia's government has called on warring parties in the conflict-torn horn of Africa nation to stop fighting during the Muslim holy month of Ramadan, a spokesman for the presidency said on Saturday.

President Sheikh Sharif Ahmed, a former Islamist rebel, said the ceasefire call was motivated by the need for peace during the religiously significant month.

"The president made this call since it is necessary to not stop people going to Islamic centres, worship Allah any time without fear, and we hope the opposition will accept it without condition," Abdulkadir Osman told Reuters by telephone.

Opposition groups said they would discuss the ceasefire call.

The President's U.N. -backed government has been facing a stubborn insurgency from the al Shabaab and Hizbul Islam rebels, dashing hopes of an end to 18 years of instability.

Western intelligence says the fighting and chaos is exploited by al Qaeda linked groups, exposing the entire region.

On Saturday clashes continued, as insurgents attacked a government-controlled Mogadishu checkpoint in the early hours.

"Al Shabaab men have attacked our positions in Ex-Control Afgoye (checkpoint). We repulsed the attackers and killed more than 10 men," Abdifatah Shaweye, deputy mayor of Banadir, told Reuters by telephone

Al Shabaab's information office denied the claim and said they took control of the base and killed nearly 10 soldiers from the government side.

Al Shabaab also said they had agreed to work together with Hizbul Islam fighters in the South Western region of Gedo.

"We had agreed to join all our forces and take orders from one command. The number of Hizbul Islam fighters (who) joined us are in the hundreds," Commander Bare Adan Khooje told Reuters.

About 100 people died last week in different parts of the country as pro-government militias and insurgents engaged in various battles. (Additional reporting by Ibrahim Mohamed in Somalia, Writing by Duncan Miriri; editing by Matthew Jones)

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