A Ukrainian man, detained this week over the bombing of mosques in central England, has also been accused of the murder of an elderly Muslim man stabbed to death on his way home from evening prayers three months ago, police said on Saturday.
The 25-year-old was arrested along with another Ukrainian man, 22, on Thursday on terrorism charges after explosions at two mosques near the city of Birmingham, one in June and the other last week.
Police said the older man was now also accused of killing Mohammed Saleem in the Small Heath area of Birmingham in April. The 75-year-old was stabbed three times in the back as he left his local mosque in what police described as a "swift, vicious attack".
"The murder of Mohammed Saleem now forms part of the wider West Midlands Counter Terrorism Unit Investigation," said Marcus Beale, Assistant Chief Constable of West Midlands Police.
The murder was being treated as an act of terrorism, the police said.
There have been several attacks on Islamic buildings in Britain since the murder of soldier Lee Rigby on a south London street in May stoked community tensions.
Birmingham, Britain's second largest city and home to a large Muslim population, has been at the forefront of concerns.
The two suspects are accused of being behind a suspected nail bomb attack on a mosque in Tipton, which took place on the same day as Rigby's funeral, and another blast at one in Walsall. Neither caused any casualties.
Police believe there was also another explosion at a third mosque in June, and offensive slogans were daubed on another Islamic centre.
On Saturday, the right-wing anti-Islamist English Defence League (EDL) held a demonstration in Birmingham which it argues is a hotbed of extremism.
Some 1,000 police were on hand to keep apart EDL supporters and anti-fascist groups holding a counter-demonstration, and four people were arrested in scuffles.