Iran’s Revolutionary Guard navy issues a warning to the United States after recent maritime incidents, while a fragile ceasefire appears to be holding. Iranian state TV reports the warning on Saturday, saying any attack on Iranian oil tankers or commercial vessels would be met with a “heavy assault” targeting one of U.S. bases in the region and enemy ships.

The warning comes a day after the United States strikes two Iranian oil tankers, according to multiple reports. The strikes raise questions about the durability of a month-old ceasefire that the U.S. says remains in effect. U.S. military statements described efforts to disable tankers attempting to breach a blockade of Iran’s ports, and earlier reported thwarting attacks on U.S. Navy ships.

Separately, Bahrain—where the U.S. Navy’s regional headquarters is based—announces arrests of dozens of people it says have links to Iran’s Revolutionary Guard. The U.S. is also awaiting Iran’s response to its latest proposal, which would aim to end the war, reopen the Strait of Hormuz to shipping, and address Tehran’s nuclear program concerns.