Qatar has announced changes to its anti-terror legislation, one of the controversial issues at the core of the crisis between Doha and its neighbours who accuse it of backing extremists.

The decree from Sheikh Tamim bin Hamad Al-Thani on Thursday establishes two national lists for individuals and terrorist entities, and sets out the requirements for being included on them.

It also defines terrorists, terrorist crimes, terrorist entities as well as the financing of terrorism.

The decree follows the signing of a US-Qatar agreement to combat terror funding, later dismissed by the Gulf nation's neighbours.

Saudi Arabia, the United Arab Emirates, Bahrain and Egypt have put in place a boycott on Qatar since June 5.

They have imposed sanctions on Doha, including closing its only land border, refusing Qatar access to their airspace and ordering their citizens back from Qatar.

They also presented the emirate with a list of 13 demands with which to comply to end the worst political crisis in the region for years.

Qatar denies the charges of extremism and has called the demands unrealistic.