Iran began restoring internet access for tens of millions of Iranians, a senior official said on Tuesday, lifting a blackout imposed after the United States and Israel launched military strikes on the country on Feb. 28.

“In line with the esteemed president’s mission and in fulfillment of the government’s promise, the first step toward free and regulated access to cyberspace has been taken,” Iran’s first vice president, Mohammad Reza Aref, wrote on social media.

NetBlocks, an internet monitoring group, said that its data showed a “partial restoration to internet connectivity” in Iran after 88 days, making it “the longest nationwide internet shutdown in modern history.”

Iranians said on social media and in messages to The New York Times that they were able to connect to the global internet after being cut off for more than 12 weeks.

The Iranian government had justified the shutdown on national security grounds, though activists argued that it was imposed to suppress communications and help the government maintain control of the population during the war.

Internet traffic coming from Iran on Tuesday appeared to be from both fixed and mobile lines, Amir Rashidi, a cybersecurity expert with Miaan, a digital rights group focused on Iran, said on social media.

“What we are seeing now is an increase in traffic from Iran,” Mr. Rashidi said in a separate text message. “Some providers have come back online, but it is still too early to say exactly what will happen.”

Mr. Rashidi pointed to another internet shutdown imposed in January during mass protests across the country, noting that, although some connectivity was restored, overall traffic only returned to 50 percent of previous levels.

The shutdown has further weakened an economy already destabilized by the conflict. Iran’s tech sector suffered heavily, facing companies forced to close and lay off staff. Iranians who sold or advertised merchandise online struggled for months to make an income.