An unusually large flotilla of merchant vessels has backed up near Yemen’s Ras Isa port in the Red Sea, after Israeli air raids damaged the tugboats needed to bring them to shore.

Several tugs were heavily damaged as a result of attacks by the Israel Defense Forces in late December. While the boats have been out of service for about three weeks, port personnel are slowly bringing tankers into harbor, causing a bottleneck, according to a worker at the terminal and a senior official in the transport ministry of Yemen’s internationally recognized government. 

Both asked not to be identified because they’re not authorized to speak publicly on the matter. At least 15 oil tankers, some of them carrying Russian fuel, have been clustered at or near the port, according to ship-tracking and Vortexa data compiled by Bloomberg.

The accumulation is emblematic of the delays that have plagued the shipping market for more than a year, adding time and costs to voyages. Persistent maritime attacks in the region, including IDF strikes on Yemeni targets and Houthi assaults on vessels in the Red Sea, have upended a vital trade route and forced many ships to divert.

Merchant vessels have been advised to halt entering Yemeni territorial waters amid reports of air strikes on January 10 across Houthi-controlled areas, including the Port of Ras Isa, according to a risk alert from the maritime security firm Ambrey. No damage to merchant ships has been reported, the firm said.

During one of IDF’s attacks on both Ras Isa and Hodeidah ports last month, 30 vessels were in the vicinity — 22 at Ras Isa and eight at Hodeidah — Ambrey said. No merchant ship was damaged, according to the security company.