Russians have overwhelmingly approved constitutional changes that could allow President Vladimir Putin to stay in office for 16 more years, electoral officials said Wednesday, though independent observers have reported widespread irregularities, AP reports.

Why it matters: This is the most significant package of constitutional changes since the fall of the Soviet Union, and will allow Putin — who has led Russia either as president or prime minister for 20 years — to serve two more terms after his current mandate ends in 2024. Critics have decried it as a power grab and cast doubt on the results.

The big picture: Elements of social conservatism — such as "faith in god" and opposition to gay marriage —will also be added into the constitution.

• Parliament will receive new powers, including the ability to appoint the prime minister, while the president will have greater control over the judicial system.
• There was no outside scrutiny of the vote, which took place over seven days, per BBC. Opposition leaders like Alexei Navalny called for a boycott of the election, while the Kremlin offered incentives to boost turnout.

Go deeper: Read Axios' special report on 20 years of Putin