The Iranian-backed Houthi rebel group in Yemen fired off attacks on Saudi Arabia Tuesday, hitting oil facilities and utilities. 

More than 70 people were injured in the attacks, which represent a major escalation in fighting between the Houthi's and an important U.S. ally, the Associated Press reported. 

The attacks targeted oil facilities associated with a shipping route connecting the Red Sea to the Gulf Aden, which Saudi Arabia uses as an alternative to the blockaded Strait of Hormuz. 

The Houthi rebels also hit "civilian and economic facilities" in Saudi cities, according to Maj. Gen. Turki al-Malki, a spokesperson for the Saudi-led coalition fighting in Yemen.

The attacks ignited fires at several oil facilities and utilities in the southern part of the country, forcing them to shut down operations, the Saudi's Energy Ministry said.