Saudi Arabia's King Abdullah on Friday replaced the head of the country's morality police, which enforces compliance to Islamic Law, at a time when some Saudis have complained that the apparatus is growing more aggressive.

No reason was given for replacing Sheikh Abdulaziz Al-Humain with Sheikh Abdulatif Al-Sheikh in the royal decree, which was announced by the state news agency.

The morality police force is known formally as the Organisation for the Promotion of Virtue and the Prevention of Vice.

Its officers patrol the country's streets making sure shops are closed at prayer times, that people are modestly dressed, and that strict gender segregation is observed.

King Abdullah announced a large increase in the morality police's budget in March. Some analysts saw the move as a reward for the religious establishment's support during the “Arab Spring” uprisings.

Some Saudis have said the organisation has grown more forceful in recent months, pointing to what they say is an increased street presence.

"What is being reported in the news shows us there is some aggressiveness. When they see something wrong they should report it to the police, not take action themselves. Society wants virtue to spread, but there should not be an invasion of people's privacy," said one human rights activist who asked not to be named.

Members of the Al-Sheikh family, who are direct descendents of Mohammed ibn Abd Al-Wahhab, the founder of Saudi Arabia's official and strict Wahhabi school of Islam, hold the titles of Grand Mufti, head of the advisory Shura Council and Islamic affairs minister.

The family is closely allied to the ruling Al-Saud family in a relationship frequently cemented through marriage.