Assailants on a motorbike killed a soldier and wounded three others in an ambush on their patrol in Yemen's restive southern province of Abyan on Tuesday, a security official said.
Witnesses said two attackers fired rocket-propelled grenades at a military vehicle in Buthayna, east of Loder, the site of violent clashes between the army and alleged al Qa'eda militants in August.
One soldier, named as Saleh Naji, was "killed in the attack and three others were wounded," the official said, blaming al Qa'eda members.
The ambush took place outside the security cordon set up by authorities in Abyan and Aden provinces for the 20th Gulf Cup, a football tournament launched on Monday, the official said.
Yemeni authorities have mobilised some 30,000 police to provide security at the stadiums and around the visiting teams' hotels.
Last week, activists of the Southern Movement, a coalition of autonomist and pro-independence groups, vowed in a statement to try to disrupt the regional football tournament.
South Yemen was independent from 1967 when the British withdrew until it united with the north in 1990. It seceded in 1994, sparking a brief civil war which ended with the region being overrun by northern troops.
Many residents complain of discrimination by the Sana'a government in the distribution of resources and the south has seen a spate of violent protests.
But the region has also been hit by growing violence involving Al-Qaeda, which has found safe haven in the south and east of Yemen, Osama bin Laden's ancestral homeland.