Jailed PKR de facto leader Anwar Ibrahim today celebrated his 70th birthday with supporters who gathered at the Kuala Lumpur High Court, where he appeared as a witness in his daughter Nurul Izzah's defamation hearing trial.

As he was driven into the KL Court complex at around 9am, he was greeted by a group of some 30 supporters who gathered to sing him the happy birthday song.

They carried a large banner with Anwar's image and a birthday greeting, along with the message: "Awak Tetap Relevan dalam Perjuangan Ini" (You remain relevant in this struggle).

The banner was signed by several pro-Anwar NGOs - Jingga 13, Anwar Ibrahim Club, Pro-Reformis 98 and #Bebas Anwar.

Anwar appeared as a witness in Nurul Izzah's defamation hearing against minister Ismail Sabri Yaakob and inspector-general of police Khalid Abu Bakar.

At around 10.30am, a heavily guarded Anwar walked into the court room to another round of birthday greetings and supporters who sang him "Allah Selamatkan Kamu".

Appearing to be in high spirits, Anwar was given the opportunity to interact with some of his supporters, including national laureate A Samad Said.

"Thank you, I received your cake," Anwar told Pak Samad.

"After 40 years old I stopped celebrating," quipped Anwar who also bantered with some of his supporters who packed the seats in the court room, under the watchful eyes of around a dozen prison officers.

"I won't tell you my age because there are too many young girls around," Anwar told a supporter, who responded by saying that his real age is already public knowledge.

Another supporter then chipped in, saying that Anwar will remain to be 40-years-old at heart until the federal opposition succeeded to capture Putrajaya.

One supporter also appeared to be taken aback when given the opportunity to shake Anwar's hand.

"Don't wash your hands for a month!" quipped another supporter as he walked out to leave the court room.

Many of the supporters waited only long enough to see Anwar and left shortly after the proceeding started before Justice Faizah Jamaluddin.

As the court adjourned for a short break, his supporters also brought out a birthday cake which will later be handed over to him.

Among others present include PKR president and Anwar's wife Dr Wan Azizah Wan Ismail; PKR lawmakers Tian Chua, Abdullah Sani Abdul Hamid and Chang Lih Kang; as well as Pro-Reformasi activists Ronnie Liu and Badrulamin Bahron.