ENTEBBE, Uganda (AFP) - Pope Francis arrived in Uganda on Friday on the second leg of a landmark trip to Africa which has seen him railing against corruption and poverty, with huge crowds celebrating his arrival.

The 78-year-old pontiff was given a rapturous welcome as he headed to the presidential palace in the central town of Entebbe, spurning a large vehicle for a small hatchback car, with waving crowds gathered along the roads, four deep in some places.

Francis arrived after three days in neighbouring Kenya, where vast crowds also turned out to an open-air mass, and where the pontiff lashed out at corruption and wealthy minorities who hoard resources at the expense of the poor.

The Pope has made humility and help for the impoverished a hallmark of his tenure.

Veteran Ugandan leader Yoweri Museveni, widely expected to be re-elected next year for his third decade in power, has said he is "honoured to host Pope Francis," saying the pontiff's "compassion for the poor and his frankness of spirit is an encouragement for all of us."

On the eve of his arrival, Ugandan MPs passed a controversial Bill giving authorities sweeping powers to regulate civil society, which rights groups say will "strangle" criticism of the government.

The legislation would grant Uganda's internal affairs ministry the power to supervise, approve, inspect and dissolve organisations in a move which could even see rights activists jailed for documenting abuses.

Street lights were draped with black, yellow and red banners, the colours of the Ugandan flag.

"This is my third pope but it can't be boring, we are blessed!" said 55-year-old Agnes Mubuya, sitting on a plastic chair on the pavement in Entebbe.

She wore a yellow dress - her Sunday best - and a laminated badge reading "Welcome Pope Francis to Uganda".

"I'd like him to talk about corruption, which is too much in Uganda. And we hope he can bring political change. He must talk to Museveni: if a pope can stand down why not a president?" Mubuya said.

Police and soldiers armed with assault rifles or batons lined the road and military pickups raced up and down streets around the presidential palace in Entebbe - some 30km south of Kampala - where Francis then met Museveni.

"This is my third pope," said 60-year old Henry Mutambo, a Protestant, as he waited on the grass verge close to the presidential palace.

"This latest pope, Francis, he cares for all the people, the whole universe, regardless of political or religious affiliation."

Security has been ratcheted up for the visit over fears Islamist rebels from Al-Qaeda's East Africa branch, the Shebab, could use the opportunity to stage attacks.

But defence chief Katumba Wamala has said measures are in place and expressed confidence "all will go as planned."

Francis has shrugged off safety fears, joking that he was "more worried about the mosquitoes".

He travels to war-torn Central African Republic (CAR) on Sunday.

"He is caring, he has mercy, he is a man of the people," said Ugandan mother Ruth Nakiboneka, 22, sitting on the grass cradling her six-week-old daughter as the papal convoy passed.

"He should focus on homosexuality to stop it, to stop child abuse, pre-marital sex and fornication and pray for good leadership," she added.

Earlier on Friday, Francis toured the Kenyan capital's Kangemi slum, his popemobile weaving through a sea of tin-roofed homes in one of the most anticipated parts of his three-day visit to Nairobi.

"I am here because I want you to know that I am not indifferent to your joys and hopes, your troubles and your sorrows," Francis told the worshippers, denouncing the "dreadful injustice of urban exclusion".

He also delivered a hard-hitting address on corruption and radicalisation on Friday in Kenya's national stadium, where thousands of smiling youngsters whooped, cheered and danced in a huge display of celebration.

"Corruption is something which eats (you) inside. It is like sugar. Sweet," he said of an issue which is of widespread concern in the east African country, that has come in for sharp international criticism over runaway graft.

"After, we finish up in a bad way... So much sugar that we either end up being diabetic, or our country ends up diabetic."

Francis also delivered a stark environmental message in Kenya, warning it would be "catastrophic" if agreement is not reached at a key UN climate summit which opens in Paris on Monday.