(Updates toll, adds details, changes dateline, byline)

By Zohra Bensemra

GHARDAIA, Algeria, Oct 2 (Reuters) - Floods caused by heavy rains have killed at least 30 people in and around the Algerian oasis town of Ghardaia, authorities said on Thursday.

The official APS state news agency quoted a senior local official as saying 50 people had been injured.

The rains died down on Thursday and water appeared to be subsiding but some streets were still submerged and residents feared more flash floods in the town of 100,000 on the northern edge of the Sahara.

Groups of youths busily shovelled sludge from the doorways of shops after two days of downpours. Some cars lay overturned by the roadside, apparently up-ended by the force of floodwaters that churned through the town.

Troops had been deployed to ensure traffic was able to move and to prevent looting, APS said, adding that eight of the 13 districts of the surrounding Ghardaia province had been affected by the floods.

Earlier Interior Minister Noureddine Yazid Zerhouni said between 300 and 600 homes had been inundated in the town, 700 km (440 miles) south of the capital Algiers.

He said gas and electricity had been cut and food stores had been waterlogged, probably spoiling them.

Ghardaia is one of several fortified Mozabite Berber medieval settlements in the M'Zab valley, a region listed as a U.N. World Heritage Site and frequented by European tourists. (Reporting by William Maclean; editing by Andrew Roche)