Mobile and fixed internet lines were cut across the country for a total of two hours, to coincide with the start of two separate school tests, AFP journalists in Algiers said.
A third hour-long internet shutdown was planned for later on Wednesday, according to a schedule issued by public operator Algerie Telecom.
Internet services were cut "in compliance with instructions from the government, aimed at ensuring the high school diploma tests run smoothly," Algerie Telecom said.
The pre-planned blackouts are due to continue for the whole period of exams, until Monday, to combat cheating among more than 700,000 students.
Ali Kahlane, president of telecoms association AOTA, said operators were required to conform to the government's demands.
The 2016 exam season was marred by widespread cheating, with exam questions published on social media before or at the start of the test.
Latecomers were banned from taking the exam and instead had to attend a specially organised test.
Electronics with internet access, such as mobile phones and tablets, were this year banned from Algeria's more than 2,000 exam centres.
Metal detectors have meanwhile been set up at the entrance to the centres, Education Minister Nouria Benghabrit said.
In a further move to prevent questions being leaked, the minister said mobile phone jammers and surveillance cameras had been installed in locations where the exam papers are printed.