King Hamad of Bahrain has signed into law a bill that imposes a strict jail sentence and a huge fine for anyone who publicly insults him.

The measure includes a jail sentence of up to seven years and a fine of up to 10,000 dinars (£16,300), which applies to "whoever has insulted, in any kind of public manner, the king of Bahrain, or its flag, or its national emblem".

Under a previous law, anyone who offended "the Emir of the country, the national flag or the national emblem" was due to be jailed – but no jail terms were set.

The Gulf Arab Island, which is also the base for the US navy Fifth Fleet, has faced increasing criticism over its human rights record in the past three years.

The Saudi-backed, ruling al-Khalifa family crushed a popular, pro-democracy uprising that started in February 2011.

Earlier this year, jailed prominent activist Zainab al-Khawaja, daughter of imprisoned human rights campaigner Abdulhadi, was sentenced to another four months in prison for an incident in May 2012, when she ripped a photo of King Hamad.

Last year, six people were sentenced to a year in prison for "insulting the King" on Twitter.

They were charged with "misusing the right of free expression" and of "undermining the values and traditions of Bahrain's society towards the king on Twitter."

Prominent Bahraini activist Nabeel Rajab, who has been at the forefront of the pro-democracy protests in the Gulf Kingdom and has more than 200,000 followers on Twitter, is serving a two-year sentence for taking part in illegal gatherings and disturbing public order.

In May 2012, the campaigner was charged in a separate case with "insulting a national institution" in comments about the interior ministry he posted on Twitter.

He was also sentenced later that year to three months in jail over different tweets he wrote about the prime minister.