Nearly 600 people have been killed in post-election violence, the Kenyan Red Cross has said, as opposition supporters protest December's vote.
HRW said Kenyan police in several cities have used live ammunition to disperse protesters and looters.
Defeated presidential candidate Raila Odinga has called for further protests.
'Looters shot'
Police have banned public gatherings since violent clashes erupted after President Mwai Kibaki was declared re-elected in a controversial poll.
"Kenyan security forces have a duty to rein in criminal violence and should protect people, but they shouldn't turn their weapons on peaceful protesters," said Georgette Gagnon, acting Africa director at HRW.
Opposition supporters are tear gasses trying to approach central Nairobi - 10 January 2008
The opposition blames President Kibaki for rigging elections
Police said they have only shot looters.
The political violence, including tribal-based clashes, have also seen 250,000 flee their homes, the United Nations estimates.
Around half-a-million people will need emergency aid, including food and shelter, the UN said.
Defeated candidate Raila Odinga and his supporters say the vote was rigged.
On Sunday, he said he was ready for talks, but only if they were led by international mediators - a condition rejected by the president.
Mr Odinga has refused to join a power-sharing administration led by Mr Kibaki and has called for three days of protests beginning on Wednesday.
"Kenyans spoke for change, Kenyans want change and Kenyans will get change," he said to some 2,000 supporters at a Nairobi church on Sunday.
"I can see the light at the end of the tunnel," he said.
Talks 'imperative'
Tuesday's reopening of parliament, where Mr Odinga's Orange Democratic Movement won 99 seats to 43 for Mr Kibaki's Party of National Unity, may provide another flashpoint for violence.
Former UN Secretary General Kofi Annan is due in Nairobi this week to head a panel to attempt to broker a deal between the two sides.
Meanwhile, the United States and the European Union said their relations with Kenya would come under review unless Mr Kibaki and Mr Odinga reach a compromise that restores stability.
The top American diplomat to Africa, Jendayi Frazer, said on Saturday that it was "imperative" that the two men sit down together "directly and without preconditions".
Source: BBC
