Saudi Arabia’s King Salman on Thursday started a five-day visit to Cairo in a show of support for Egyptian President Abdel Fattah al-Sisi, with the leaders due to sign a raft of investment deals.

Saudi Arabia has been the key backer of Sisi since the then-army chief in 2013 overthrew his Islamist predecessor Mohamed Mursi, whose Muslim Brotherhood movement was viewed with suspicion by Riyadh.

It has pumped billions of dollars in aid and investment into Egypt's battered economy, and the two heads of state are expected to ink more investment agreements on Friday amounting to about $1.7bn.

Live footage on state television showed Sisi greeting King Salman at Cairo airport, before heading off in a convoy to the presidential palace.

The two will hold meetings later in the day and on Friday, when they will sign 14 agreements that include a $1.5bn deal to invest in the Sinai Peninsula, an Egyptian government official said.

King Salman is expected to address the Egyptian parliament on Sunday, state media reported.

Egyptian media gave full coverage of the visit, with state television welcoming the Saudi king to his "second country" and playing celebratory music as his plane touched down in Cairo.

"This is the first official visit by King Salman, whose valuable and honourable positions in support of Egypt and its people will never be forgotten," the presidency said in a statement.

"Egypt accords great importance to this visit," it said, adding the leaders would discuss regional issues and economic cooperation.

The visit follows months of reports in both Saudi and Egyptian newspapers of strained ties over Cairo's unwillingness to participate fully in Saudi-led military operations in Yemen.

Egypt had announced it would join the operations against Iran-backed Shia rebels in Yemen with ground troops if needed, but appears to have balked at the prospect of becoming mired in the conflict.

However, Saudi Arabia has played a key role in propping up Egypt's economy, whose vital tourism industry has been devastated by years of political turmoil and jihadist attacks.