BAGHDAD (AFP) - Ten Iraqi policemen and four American soldiers were killed in a spate of roadside bomb attacks across the country on Tuesday, in the bloodiest day for the US military in five months. The blasts followed a series of bombings on Monday that left 22 people dead nationwide, on what was the worst day of violence since the Muslim holy month of Ramadan began more than two weeks ago. The US deaths in northern Iraq and in Baghdad culminated in the highest number of American soldiers killed on a single day since April 10, when five died in a truck bomb attack in Mosul. Three of the Americans died when a homemade bomb struck their patrol in the north of the country, a US army statement said without giving further details. The fourth US soldier was killed by a similar explosive device while on patrol in southern Baghdad. The latest deaths take to 4,342 the number of US troops killed since the US-led 2003 invasion, according to an AFP tally based on the independent website US combat troops withdrew from Iraqi towns, cities and villages on June 30 but they still operate in urban areas under the authority of the Iraqi security forces. Earlier on Tuesday, a northern Iraqi police chief and nine other officers were killed in a series of roadside bomb attacks targeting patrols near the restive oil hub city of Kirkuk, officials said. Lt-Col Zaid Hussein, the top-ranking officer in Amerli town, and three colleagues died when a roadside bomb struck their convoy, said Col Hussein al-Baiti, a senior officer in Kirkuk. Four more police were killed when a roadside bomb struck their patrol in the south of the province, Baiti said. A third roadside bomb killed two officers working as a protection force on a main road near the town of Daquq, also south of Kirkuk, and wounded two of their colleagues, a second police official said. In Baghdad, meanwhile, a sticky bomb attached to a car exploded in the east of the capital, killing at least one person and leaving 12 others hurt, police said. The latest casualties come after the number of violent deaths in Iraq hit a 13-month high in August, raising fresh concerns about stability after the government admitted that security is worsening. Statistics compiled by the defence, interior and health tries showed that 456 people - 393 civilians, 48 police and 15 Iraqi soldiers - were killed in the highest monthly toll since July 2008 when 465 died in unrest. Last months high toll was partly explained by twin truck bomb attacks on the finance and foreign ministries in Baghdad that killed at least 95 people and wounded 600 others on August 19. Those attacks triggered a diplomatic crisis when Prime Minister Nuri al-Maliki blamed neighbouring Syria for failing to hand over two of the alleged planners of the finance ministry bombing. Maliki sent extra troops to western Iraq at the weekend to secure the border with Syria, whose President Bashar al-Assad has dismissed allegations that Damascus was harbouring terrorists as immoral and politically motivated. The United States has also accused Syria of having lax border controls that allow insurgents, including rebels linked to Al-Qaeda, to cross into Iraq.